TS2712EN

Troubleshooting
Manual

Allison Transmission
Electronic Control

OCTOBER 1994

Division of General Motors Corporation

P.O. Box 894 Indianapolis, Indiana 46206-0894
www.allisontransmission.com

Printed in U.S.A.

1994 General Motors Corp.

ALLISON TRANSMISSION ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

NOTE
This publication is revised periodically to include improvements, new models,
special tools, and procedures. Revision is indicated by letter suffix to publication
number. Check with your Allison Transmission service outlet for currently
applicable publication. Additional copies of this publication may be purchased
from authorized Allison Transmission service outlets. See your yellow pages
under EnginesDiesel or TransmissionsTruck, Tractor, etc.

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

I M P O R T A N T

S A F E T Y

N O T I C E

It is your responsibility to be completely familiar with the warnings and cautions described in this manual.
These warnings and cautions advise against the use of specific service methods that can result in personal
injury, damage to equipment, or cause the equipment to be unsafe. It is, however, important to understand that
these warnings and cautions are not exhaustive. Allison Transmission could not possibly know, evaluate, and
advise the service trade of all conceivable ways in which service might be done or of the possible hazardous
consequences of each way. Consequently, Allison Transmission has not undertaken any such broad evaluation.
Accordingly, ANYONE WHO USES A SERVICE PROCEDURE OR TOOL WHICH IS NOT
RECOMMENDED BY ALLISON TRANSMISSION MUST first be thoroughly satisfied that neither personal
safety nor equipment safety will be jeopardized by the service methods selected.
Proper service and repair is important to the safe, reliable operation of the equipment. The service procedures
recommended by Allison Transmission and described in this service manual are effective methods for
performing service operations. Some of these service operations require the use of tools specially designed for
the purpose. The special tools should be used when and as recommended.

WA R N I N G S ,

C A U T I O N S ,

A N D

N O T E S

Three types of headings are used in this manual to attract your attention.
WARNING: Is used when an operating procedure, practice, etc., which, if not correctly followed, could result
inpersonal injury or loss of life.

CAUTION: Is used when an operating procedure, practice, etc., which, if not strictly observed, could result in
damage to or destruction of equipment.
NOTE:

Is used when an operating procedure, practice, etc., is essential to highlight.

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

FOREWORD (How to Use This Manual)
This manual provides the technician with the most current information for troubleshooting the Allison
Transmission Electronic Control.
There are two generations of Electronic Control. This document focuses on the first generation. It covers the
following on- and off-highway transmission models:
On-Highway

Off-Highway

MT(B) 648
HT(B) 741, 746 and 748
HT(B) 755CR and 755DR
V 731, V 731RH, VR 731,
VR 731RH

CLBT 5962 and 6062

DP 8963
CL(B)T 9681
CLT 755 and CL(B)T 755

Allisons second generation Electronic Control is mandatory for all Allison World Transmissions. Refer to the
World Transmission Troubleshooting Manual when troubleshooting WT transmissions.
This manual is divided into sections and includes:
Definitions and descriptions of commonly used terms and abbreviations.
An overview of system operation.
Component installation and adjustment procedures.
Vehicle interface wiring procedures and a description of available electronic options.
A description of the systems self-diagnostic capabilities.
Detailed procedures for troubleshooting diagnostic codes.
Procedures for troubleshooting intermittent diagnostic codes.
Troubleshooting procedures when codes are not present.
Additional information regarding connector and terminal repair, connector terminal designations, and
hydraulic and electrical schematics.
To be an effective troubleshooter, you must understand how the Electronic Control operates. Review the
Operational Overview, Component Installation and Adjustment, Vehicle Interface and Electronic Options, and
Self-Diagnostics sections carefully.
Once you understand system components and operation, refer to the appropriate troubleshooting section (Codes
Present, Intermittent Codes, or No Codes). Each section overviews the troubleshooting process, and explains how
to proceed using additional information located in the Appendices.
In some instances, you may need to refer to specific Repair Manuals or Parts Catalogs for the latest repair
procedures and replacement part numbers. Service Information Letters (SILs) are sometimes published to
provide additional service information. Use these resources to stay informed and updated.

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ALLISON TRANSMISSION ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

TABLE OF CONTENTS
DEFINITIONS AND ABBREVIATIONS ..................................................................................... v
OPERATIONAL OVERVIEW
Introduction ............................................................................................................................................
Applications ...........................................................................................................................................
Electronic Control Unit (ECU) ..............................................................................................................
Programmable Read Only Memory (PROM) ........................................................................................
Output Speed Sensor ..............................................................................................................................
Throttle Position Sensor .........................................................................................................................
Shift Selectors ........................................................................................................................................
Reverse and Forward Pressure Switches................................................................................................
Oil Pressure Switches/Sensors ...............................................................................................................
Temperature Sensor................................................................................................................................
Chassis Wiring Harness..........................................................................................................................
Cab Wiring Harness ...............................................................................................................................
Secondary Wiring Harness .....................................................................................................................
Electro-Hydraulic Valve Body ...............................................................................................................
Solenoids ................................................................................................................................................
Typical On-Highway Fluid Flows..........................................................................................................
Typical Off-Highway Fluid Flows .........................................................................................................

1-1
1-2
1-3
1-4
1-5
1-6
1-8
1-9
1-10
1-12
1-13
1-14
1-15
1-16
1-17
1-19
1-29

COMPONENT INSTALLATION AND ADJUSTMENT

Introduction ............................................................................................................................................
Electronic Control Unit (ECU) ..............................................................................................................
Programmable Read Only Memory (PROM) ........................................................................................
Output Speed Sensor ..............................................................................................................................
Throttle Position Sensor .........................................................................................................................
Shift Selectors ........................................................................................................................................
Wiring Harnesses ...................................................................................................................................

2-1
2-2
2-3
2-4
2-5
2-8
2-11

VEHICLE INTERFACE
Introduction ............................................................................................................................................
Electronic Control Inquiry System.........................................................................................................
Mandatory Vehicle Interface ..................................................................................................................
Optional Cab Harness Interface .............................................................................................................
Optional Secondary Harness Interface...................................................................................................

3-1
3-1
3-2
3-12
3-28

SELF-DIAGNOSTICS .................................................................................................................... 4-1

TROUBLESHOOTINGTROUBLE CODES PRESENT .......................................................... 5-1
TROUBLESHOOTINGINTERMITTENT TROUBLE CODES ............................................. 6-1
TROUBLESHOOTINGNO TROUBLE CODES PRESENT ................................................... 7-1

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ALLISON TRANSMISSION ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

TABLE OF CONTENTS
APPENDIX ATROUBLESHOOTING STEPSTROUBLE CODES PRESENT................... A-1
APPENDIX BTROUBLESHOOTING STEPSNO TROUBLE CODES PRESENT............ B-1
APPENDIX CCONNECTOR, TERMINAL, AND WIRE REPAIR ........................................ C-1
APPENDIX DADDITIONAL TERMINAL DESIGNATIONS................................................. D-1
APPENDIX EELECTRICAL SCHEMATICS ........................................................................... E-1
APPENDIX FHYDRAULIC SCHEMATICS ............................................................................. F-1
APPENDIX GSPECIAL TOOLS................................................................................................. G-1
APPENDIX HDIAGNOSTIC CODE BACKGROUND INFORMATION.............................. H-1

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

DEFINITIONS AND ABBREVIATIONS
Allison Transmission Electronic Control System The complete electronic control system for the
transmission, including all detail components.
Bi-Directional Communication Link (BDCL) Hard wire connections which allow the Allison Electronic
Control system to communicate with other engine or transmission controls.
Check Transmission Light Optional instrument panel warning light that alerts the operator that a problem has
occurred and the vehicle should be serviced as soon as possible. Also used by the technician to read diagnostic
codes when a diagnostic data reader is not used.
Detroit Diesel Electronic Controls (DDEC) Detroit Diesels electronic engine control system.
Diagnostic Codes (Trouble Codes) Two-digit codes stored in the electronic control ECU memory. These
codes are set when system self-diagnostics detects problems. Technicians access codes and use them to help
troubleshoot problems.
Diagnostic Data Link (DDL) Cab harness connector which allows a diagnostic data reader to interface with
the Allison Electronic Control system.
Digital Display Unit (DDU) Optional electronic component that displays various system operating and
warning information.
Digital Volt Ohmmeter (DVOM) Electrical device used for performing voltage, continuity and
resistance tests.
Do Not Shift Light Warning lamp located on the shift selector. This indicator alerts the driver that a
potentially serious problem has been detected and shift selection has been limited.
Electronic Control Inquiry System (ECIS) On-line data base (available through Distributor Parts
Departments) that indicates which options are programmed on a particular PROM.
Electronic Control Unit (ECU) The Allison Electronic Control system onboard microcomputer. This is the
electronic brain for the system.
Fluidic Oil Level Sensor (FOLS) One of the three types of switches that signal the ECU when a low lube
pressure or low oil level condition exists. The FOLS uses a separate housing that bolts to the bottom of the valve
body. It is very similar to the Low Oil Pressure/Level Sensor, but does not use a bi-metal strip.
Infinity () An indication that circuit or component resistance is so high it can not be measured. Generally,
this means continuity is not present (the circuit is open).
Jumper Wire A short piece of wire used to connect two electrical circuits or bypass a portion of a circuit.
Low Oil Level/Pressure Sensor One of the three types of switches that signal the ECU when a low lube
pressure or low oil level condition exists. The Low Oil Level/Pressure Sensor uses a separate housing that bolts to
the bottom of the valve body. It is very similar to the Fluidic Oil Level Sensor and uses a bi-metal strip to
compensate for cold oil temperatures until the transmission warms up.
Lube Pressure Switch One of the three types of switches that signal the ECU when a low lube pressure or
low oil level condition exists. The Lube Pressure Switch is configured like the forward and reverse pressure
switches. It plumbs directly into the lubrication oil passage.
Ohm () A unit of electrical resistance measurement.

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

DEFINITIONS AND ABBREVIATIONS
Options Programmed special features. Examples Bed Hoist Interlock, Loading Hold, Neutral-To-Range
Inhibit, etc. Options must be programmed in the PROM and properly wired.
Programmable Read Only Memory (PROM) This is the microchip that contains all the transmission shift
and control information. The PROM is located in the ECU.
Power Take-Off (PTO) Transmission-mounted accessory drive unit. PTOs are used to operate pumps and
other accessories on specialty vehicles.
Self-Diagnostics The Allison Transmission Electronic Controls built-in capability to recognize
system problems.
Solenoid Components in the electro-hydraulic valve body that act as switches to direct hydraulic pressure into
specific passages or to exhaust.
Speed Sensor (Output Speed Sensor) Provides the electronic control system with output speed information.
The speed sensor replaces the conventional hydraulic governor system.
Splice A connection of two or more wires. When repairing harness wires, they are spliced using special
butt connectors.
Temperature Sensor Monitors sump oil temperature for the ECU. On-highway sensors are mounted on
the solenoid control circuit (on the internal wiring harness). Off-highway sensors are mounted in the lock-up
valve body.
Throttle Position Sensor (TPS) Provides the electronic control system with throttle position information. The
TPS replaces the conventional hydraulic modulator system.
Transmission Engine Communication Link (TECL) A type of Bi-Directional Communication Link
(BDCL) that allows the Allison Transmission Electronic Control to communicate with engine controls.
Transmission Test Switch Vehicle manufacturer-installed switch that places the electronic control system in
its diagnostic mode. When the switch is on, trouble codes can be retrieved.
Transmission to Transmission Communication Link (TTCL) A type of Bi-Directional Communication
Link (BDCL) that allows the Allison Transmission Electronic Control to communicate with other
transmission controls.
Vehicle Interface Term describing the electrical connections between the vehicle and the Allison
Transmission Electronic Control system.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
INTRODUCTION
The Allison Transmission Electronic Control provides the shifting thought process for several Allison
transmissions. Electronically-controlled transmissions use the same clutch and planetary gear components as
conventional transmissions, but utilize a digital electronic system to control the transmission hydraulics.
The Electronic Control uses an electro-hydraulic valve body. The hydraulic circuits within the electro-hydraulic
valve body are controlled by solenoids. These solenoids take the place of conventional on-highway shift
signal valves and off-highway solenoids. They are switched on and off by signals from the Electronic Control
Unit (ECU).

SPEED
SENSOR

SHIFT
SELECTOR

THROTTLE
POSITION
SENSOR

ECU

SOLENOIDS

ELECTRO-HYDRAULIC VALVE BODY

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Electronic Control System

The Electronic Control needs sensing input. Speed sensor input replaces governor pressure. Throttle position
sensor input replaces on-highway modulator pressure. Mechanical shift selector components are replaced by
electronic push button or lever selectors. And the Electronic Control Unit (ECU) also receives input from a
temperature sensor and various pressure switches.
The Electronic Control can be designed with a variety of operational options. Hard wiring between the
Electronic Control and the vehicle is called interface. Some interface wires provide input signals to the ECU,
often to enable a specific option. Other interface wires are used for signals sent from the ECU to various
Electronic Control and vehicle components. The entire system communicates and interfaces through a series
of wiring harnesses.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
APPLICATIONS
The transmission model number indicates when a transmission is equipped with the Electronic Control.
On-highway models that are equipped with the Electronic Control include the following:
MT(B) 648
HT 746
HT(B) 741 and HT(B) 748
HT(B) 755CR and HT(B) 755DR
V 731, V 731RH, VR 731, and VR 731RH
These units are commonly found in delivery, refuse, bus, and emergency vehicles.
The following off-highway models are equipped with the Electronic Control:
CLBT 5962 and 6062
DP 8963
CL(B)T 9681
CL(B)T 755
These units are often found in dump trucks, scrapers, oil field equipment, and agricultural and logging vehicles.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
ELECTRONIC CONTROL UNIT (ECU)
The ECU is an onboard microcomputer. It receives information through a wiring harness from a variety of
sources. Based on this information and the system configuration, the ECU controls special features and
determines how and when shifts occur.

CHASSIS
HARNESS
J1
CAB
HARNESS
J2

CAB HARNESS
J1A
CHASSIS
HARNESS
J1B

SPLASHPROOF ECU

SEALED-STANDARD ECU

CAB HARNESS
J1A
SECONDARY
MODE HARNESS
J3

CHASSIS
HARNESS
J1B

SEALED-PLUS II ECU

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Types of ECUs
There are three types of ECUs:
Splash Proof - this is the earliest model, no longer in production.
Sealed Standard - replaced the Splash Proof model.
Sealed Plus II - this unit includes an additional connector to accommodate a secondary shift selector and
capabilities for additional special features.
The ECU is a sealed component. The only field service performed on the ECU is Programmable Read Only
Memory (PROM) chip replacement. The ECU has self-diagnosis capabilities - if an Electronic Control problem is
detected, the ECU can store pertinent information in the form of diagnostic codes.

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OPERATIONAL OVERVIEW
PROGRAMMABLE READ ONLY MEMORY (PROM)
The PROM is the ECUs data bank. Different PROMs are available for a wide variety of vehicle and equipment
applications and special features.

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PROM and Retainer (top), PROM (bottom)

The PROM is located inside the ECU, accessed through a cover in the ECU case. PROMs with specific features
are available from Allison, and installing the wrong PROM can alter the Electronic Control performance.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
OUTPUT SPEED SENSOR
The output speed sensor provides the Electronic Control with output speed information. It replaces the
conventional hydraulic governor system and is located at the rear of the transmission.

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On-Highway Output Speed Sensor (top) and Off-Highway Output Speed Sensor (bottom)
The output speed sensor has a magnetic pick-up that reads the movement of a speed sensor gear located on the
transmission output shaft. Output shaft rotation causes the speed sensor gear teeth to pass through a magnetic
field at the end of the sensor. As each tooth passes, it creates an electrical pulse which is directed to the ECU. The
ECU uses this signal to help control upshifts, downshifts, retarder application and lock-up clutch application.
The on-highway speed sensor uses a 16-tooth gear, and the off-highway speed sensor uses 39 or 41-tooth gears,
depending on transmission model.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
THROTTLE POSITION SENSOR
The throttle position sensor replaces the conventional hydraulic modulator pressure valve and related circuits. It
consists of a pull actuation cable and a linear potentiometer. One end of the cable is attached to the engine fuel
lever and the other end is attached to the potentiometer inside the sensors protective housing.

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Throttle Position Sensor and Cable

Throttle movement causes a change in the electronic signal to the ECU. The ECU is programmed to recognize the
signal as percent of throttle. The sensor linear potentiometer converts throttle movement into a voltage signal.
As the wiper moves across the resistive strip, resistance changes, varying the voltage the ECU sees or counts.
255 COUNTS

0 COUNTS

233 COUNTS

14 COUNTS

APPROX.
0.75 INCH
STROKE

ERROR
ZONE

IDLE
0

0.2 INCH

ERROR
ZONE

FULL
THROTTLE
1.8 INCHES

1.9 INCHES

APPROX.
0.5 INCH
FULLY
RETRACTED

FULLY
EXTENDED

TPS Movement and Electronic Counts

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
THROTTLE POSITION SENSOR
The throttle position sensor produces anywhere from 0 to 255 counts, although its actual movement is only a
small area within those counts (total sensor travel is about 2 inches, but actual sensor travel when properly
installed is only about 3/4 inch). If the sensor produces 233 or more counts at idle, it is said to be in an error
zone. If the sensor produces 14 or fewer counts at full throttle, the sensor is within an error zone. Either of these
conditions logs a diagnostic code in the ECU memory and causes full throttle shift points.
Once initial adjustment is performed, the throttle position sensor is self-adjusting. Every time the vehicle is
started and the ECU is initialized, the sensor is re-calibrated. The ECU stores the sensor readings at vehicle
shut-down. When the ECU is powered, idle counts are decreased by 15 from the previous reading, and full
throttle counts are increased by 15 from the previous reading. This narrowed count band is widened once the
operator steps on the throttle. The ECU reads actual sensor travel and continually re-adjusts to the highest and
lowest counts it sees. This compensates for minor cable, mounting, and component wear.
When the throttle is wide open, the ECU commands upshifts to occur near the engine governed speed. Part
throttle causes upshifts to occur at lower engine speeds. The difference between full throttle and part throttle
upshifts is determined by the shift calibration in the PROM.
NOTE:

When the Allison Transmission Electronic Control is interfaced with DDEC, both systems share
the same throttle position sensor signal (from the engine). DDEC II sensor interface is provided
by a non-Allison supplied interface module. Two levels of DDEC II interface are available, a
Basic Interface (which provides only throttle position sensor information) and a Maximum
Feature Interface (which provides additional communication signals). Refer to the Vehicle
Interface section of this manual for more information.

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OPERATIONAL OVERVIEW
SHIFT SELECTORS
The Electronic Control uses two general types of shift selectors -push button and lever.

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Push Button Shift Selector

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Lever Shift Selector

Earlier push button selectors had a membrane switch, and new style selectors use a snap dome switch.
Lever selectors operate using Hall Effect magnetic switches. The Hall Effect switch is a sensor which detects a
magnetic field. The magnetic system responds to the physical quantity to be sensed in our case, the position of
the lever shift selector. General features include true solid state, long life, contactless operation and broad
temperature range. The lever selector has up to eight positions, and shift patterns and detent mechanisms vary
between applications. These electronic components replace conventional shift selector mechanisms and linkages.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
REVERSE AND FORWARD PRESSURE SWITCHES
The on-highway Electronic Control uses pressure switches to communicate signals to the ECU.
Reverse and forward pressure switches indicate when the transmission is in reverse or a forward range. They can
be either of two styles (threaded and bolt down) and plumb directly into clutch apply circuits.

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Threaded and Bolt-Down Pressure Switches

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
OIL PRESSURE SWITCHES/SENSORS
The oil pressure switch signals the ECU when a low lube pressure or low oil level condition exists. There are
three different types of oil pressure switches the lube pressure switch, the low oil level/pressure sensor and the
fluidic oil level sensor. The transmission will only be equipped with one of these switches. The transmission
assembly number determines the original switch for the transmission, but the parts catalog identifies the latest
switch available for service. The PROM and the chosen switch must be compatible (the PROM must be
programmed for the type of switch used).
The lube pressure switch is configured like the forward and reverse pressure switches and plumbs directly into a
lubrication oil passage. The lube pressure switch is normally open, and lube pressure closes the switch.
When lube pressure is low, the switch opens. When other relevant parameters have been met, this generates a
trouble code.

COLD OIL TEMP

NORMAL OIL TEMP

PROPER OIL LEVEL

NORMAL OIL TEMP

LOW OIL LEVEL
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Low Oil Level/Pressure Sensor

The low oil level/pressure sensor uses a separate housing that bolts to the bottom of the valve body. An orifice in
the sensor housing produces a pressurized stream of oil that is directed to a switch on the opposite side of the
housing. A bi-metal strip compensates for oil level changes as the transmission warms up. The strip blocks the
flow of pressurized oil until the oil is warm. This allows the oil level to rise before a trouble code is generated. As
the transmission warms, the bi-metal strip moves out of the way. The low oil level/pressure sensor is normally
open, and if oil still reaches the switch after the transmission is warm, the switch closes, generating a code.
Pressurized oil can only reach the switch if the warm oil level in the pan is too low. If the oil level is correct, it
blocks the flow of pressurized oil.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
PRESSURE SWITCHES/SENSORS

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Fluidic Oil Level Sensor

The fluidic oil level sensor is similar to the low oil level/pressure sensor. The primary physical difference is the
absence of the bi-metal strip. The ECU is programmed to ignore low oil level signals until the temperature sensor
indicates the oil in the sump is warm. This eliminates the need for the bi-metal strip. The fluidic oil level sensor is
normally closed, and when pressurized oil contacts the pressure switch during normal operating temperatures, the
switch contacts open, generating a trouble code.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
TEMPERATURE SENSOR
The temperature sensor is part of the internal valve body wiring harness and monitors sump oil temperature for
the ECU. On-highway sensors are mounted in the internal wiring harness. Off-highway sensors are mounted in
the lockup valve body.

TEMPERATURE
SENSOR
(ON HIGHWAY)
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Temperature Sensor
When oil temperature is below -25 degrees (F), all shifts are blocked. When oil temperature is between -25
degrees (F) and 25 degrees (F), transmission shifting is limited to neutral, 1st and reverse. Above 270 degrees (F),
the Hot light comes on (if equipped), a trouble code is stored in memory and the highest gear is blocked for
on-highway models. The highest two gears are blocked for off-highway models. Some applications (emergency
vehicles, for example) are often exempt from shift inhibit during temperature extremes, but the Check
Transmission light may still come on and codes may be logged in the ECU memory.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
CHASSIS WIRING HARNESS
The chassis harness connects the throttle position sensor, output speed sensor and electro-hydraulic valve body
to the ECU.

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Bulkhead Connector, ECU Connector, Output Speed Sensor Connector, and the TPS Connector
(from left to right)
Special connectors allow the harness to plug into each component. The wire numbers within the chassis harness
are all 100 series numbers (111, 114, etc.).

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
CAB WIRING HARNESS
The cab harness connects the shift selector and interface components to the ECU. The wire numbers within the
cab harness are all 200 series wires (201, 224, etc.).

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Shift Selector Connector, ECU Connector, and DDL Connector (from top to bottom)
The harness can include loose interface wires, or a factory-supplied interface connector. The Diagnostic Data
Link (DDL) connector is part of the cab harness. Service personnel can plug a diagnostic reader into this
connector to monitor trouble codes and system operation.
The cab harness also includes Bi-Directional Communication Link (BDCL) wires. BDCL allows the Electronic
Control to communicate with DDEC I equipped vehicles.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
SECONDARY WIRING HARNESS
The Sealed Plus II ECU is equipped to handle several additional optional features. These options are
wired through the secondary harness. The wire numbers within the secondary harness are all 300 series
wires (309, 317, etc.).

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Secondary Harness and Connector

The secondary harness can also connect a secondary shift selector to the ECU. The secondary wiring harness is
only used on Sealed Plus II ECUs.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
ELECTRO-HYDRAULIC VALVE BODY
An Electronically-Controlled transmissions hydraulic circuits and valves are controlled by a series of solenoids
mounted on the transmissions electro-hydraulic valve body. These solenoids are activated and deactivated by
electrical signals generated by the ECU.

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Typical On-Highway Solenoids

The on-highway valve body also contains the forward and reverse pressure switches and one type of oil level or
pressure sensor (lube pressure switch, low oil level/pressure sensor or fluidic oil level sensor).

B
C

D
E
F

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Typical Off-Highway Solenoids

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
SOLENOIDS
Solenoids in the electro-hydraulic valve body act as switches to direct hydraulic pressure into specific passages or
to exhaust. Each solenoid is positioned on the valve body so that solenoid pressure flows to its inlet port.
DE-ENERGIZED

ENERGIZED

PLUNGER

EXHAUST

MAIN

CHECK BALL

MAIN

CHECK BALL
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Solenoid (sectional view) On-Highway

The inlet port is regulated by check ball position. When the solenoid is de-energized, the check ball is held down
by a plunger, blocking the oil pressure port. In this position, solenoid pressure located above the ball exhausts.
When the solenoid is electrically energized, the plunger moves up, allowing the check ball to move. This blocks
the exhaust port and allows oil pressure to pass through.
The Electronic Control uses two general types of solenoids - latching and non-latching. When latching solenoids
are energized, they move one direction and stay there until they receive another signal. Only a short application of
power is required to position the solenoid and it stays in that position until it is energized again.
Non-latching solenoids require constant power to remain in position. When power is applied, the non-latching
solenoid moves into position and stays there as long as it remains energized.
On-highway solenoids can be either latching or non-latching. Off-highway solenoids are always non-latching.
NOT ENERGIZED SOLENOID
SOLENOID
FEED
PRESSURE

ENERGIZED SOLENOID
SOLENOID
FEED
PRESSURE

EX

ORIFICE

EX

ORIFICE

EX

EX
EX

EX

EX

EX

Solenoid and Shift Valve (sectional view) Off-Highway

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
SOLENOIDS

CLAMP DOWN

BOLT DOWN

2120647.70
12/15/92

Latching Solenoids On-Highway

On-highway solenoids are either bolted or clamped to the valve body. Clamped solenoids are sandwiched
between the valve body and a mounting plate. Bolted solenoids are secured to the valve body with torx-head
screws.
On-highway clamp down latching solenoids are identified by a single tab at the solenoid base. Bolt down latching
solenoids have a tab centered between the two bolt holes.

CLAMP DOWN

BOLT DOWN

2120647.71
12/15/92

Non-Latching Solenoids On-Highway

On-highway clamp down non-latching solenoids have two tabs on their base. Bolt down non-latching solenoids
have a tab slightly off-center between the two bolt holes.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
TYPICAL FLUID FLOWS - ON-HIGHWAY OVERVIEW
Component Description and Configuration
The Electronic Control sensors eliminate the need for conventional hydraulic governor pressure, modulator
pressure and selector valves. The output speed sensor provides the ECU with output speed information, the
throttle position sensor provides throttle position information, and electronic shift selectors provide operator
input. Based on these signals, plus vehicle interface and oil pressure, temperature and level input, the ECU
energizes and de-energizes solenoids in the electro-hydraulic valve body.
Conventional shift signal valves are replaced by latching solenoids in the electro-hydraulic valve body. These
solenoids control the position of shift valves. Shift valves control hydraulic flow in the transmission clutch-apply
circuits. During a shift, shift valve movement exhausts the applied clutch and applies the oncoming clutch.
The neutral range valve is controlled by one latching and one non-latching solenoid. In neutral, this valve blocks
the flow of main pressure to the forward/reverse valve. In range, the valve allows main pressure to the
forward/reverse valve. The neutral range valve controls the transmission shifts from neutral to a range, and from a
range back to neutral.
The forward/reverse valve is controlled by a latching solenoid. Depending on the solenoid position and the
neutral range valves position, the forward/reverse valve directs main pressure into either the fourth or forward
clutch apply circuit. The forward/reverse valve controls whether the transmission shifts into a forward range
or reverse.
The electro-hydraulic valve body uses trimmer valves to regulate oncoming clutch application. The trimmer
regulator valve controls pressure under the trimmer valve plug, regulating trimmer valve operation. The trimmer
regulator valve is controlled by a non-latching solenoid.
The lockup relay valve is controlled by a non-latching solenoid. Depending on solenoid position, the lockup relay
valve exhausts or applies the lockup clutch apply circuit.
The solenoids, neutral range valve and trimmer regulator valve all receive continuous main pressure from the
solenoid priority valve and direction priority valve. These valves ensure a steady flow of main pressure regardless
of transmission range or activity.
Each solenoid is designated by letter. Latching solenoids A, B, C and D control shift valves. In five-speed
models, solenoid A controls the low-1 shift valve, solenoid B controls the 1-2 shift valve, solenoid C controls the
2-3 shift valve and solenoid D controls the 3-4 shift valve. In four-speed models, solenoid A is not used and
solenoids B, C, and D control the same shift valves. In three-speed models, solenoids A and B are not used.
Solenoid C controls the 1-2 shift valve and solenoid D controls the 2-3 shift valve.
Non-latching solenoid E controls trimmer regulator valve position.
Latching solenoid F controls forward/reverse valve position. Non-latching solenoid G controls the position of the
lockup relay valve. Non-latching solenoid H controls main pressure flow to the bottom of the neutral range valve,
and latching solenoid J controls main pressure flow to the top of the neutral range valve.
NOTE:

The following fluid flow description is based on a typical, four-speed, on-highway electronicallycontrolled transmission. Although some components vary slightly between models, the same
operating principles apply.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
NEUTRAL FLUID FLOW (ON-HIGHWAY)

MAIN
FORWARD
REVERSE
VALVE

NEUTRAL
RANGE VALVE

MAIN

EX

EX

EX

EX

FWD.
CLUTCH

EX

FOURTH
CLUTCH

EX

EX

EX

EX

SECOND
CLUTCH

EX

EX

THIRD
CLUTCH

B
EX

FIRST
CLUTCH

EX

EX

EX

EX

2-3 SHIFT VALVE

EX

EX
C

1-2 SHIFT VALVE

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5/27/93

In Neutral, solenoid J is energized. Solenoids B, C, D and F are not energized.

When the vehicle is started, main pressure from the solenoid priority valve feeds all the solenoids. Main pressure
from the neutral range valve flows to the direction priority valve and finally to the shift valves. Main pressure
cascades downstream from the direction priority valve through the 2-3 shift valve and the 1-2 shift valve into
the first-clutch apply circuit.
In neutral, J is the only energized solenoid. It directs main pressure to the top of the neutral range valve, which,
along with spring pressure, keeps the neutral range valve positioned down. This causes main pressure to
deadhead at the neutral range valve. Main pressure cascading through the 2-3 shift valve and the 1-2 shift valve
keeps first clutch applied. Since only first clutch is applied, the transmission is in neutral.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
FIRST RANGE FLUID FLOW (ON-HIGHWAY)
MAIN
FORWARD
REVERSE
VALVE

NEUTRAL
RANGE VALVE

MAIN

EX

EX

EX

EX

FWD.
CLUTCH

EX

FOURTH
CLUTCH

EX

EX

EX

EX

SECOND
CLUTCH

EX

EX

THIRD
CLUTCH

B
EX

FIRST
CLUTCH

EX

EX

EX

EX

2-3 SHIFT VALVE

EX

EX
C

1-2 SHIFT VALVE

2120647.73
5/27/93

In First Range, solenoids F and H are energized. Solenoids B, C, D and J are not energized.
When the transmission is shifted into drive or first range, solenoid J is de-energized and solenoids H and F are
energized. Solenoid H directs main pressure to the bottom of the neutral range valve. Since solenoid J is no
longer energized, main pressure on top of the neutral range valve is exhausted, allowing the neutral range valve to
move up. This allows main pressure from the solenoid priority valve to flow through the neutral range valve to
the forward/reverse valve. Main pressure from solenoid F has the forward/reverse valve positioned up. This
allows main pressure from the neutral range valve to flow through the forward/reverse valve into the forwardclutch apply circuit, applying forward clutch. First clutch remains applied, resulting in first range.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
SECOND RANGE FLUID FLOW (ON-HIGHWAY)

MAIN
FORWARD
REVERSE
VALVE

NEUTRAL
RANGE VALVE

MAIN

EX

EX

EX

EX

FWD.
CLUTCH

EX

FOURTH
CLUTCH

EX

EX

EX

EX

SECOND
CLUTCH

EX

EX

THIRD
CLUTCH

B
EX

FIRST
CLUTCH

EX

EX

EX

EX

2-3 SHIFT VALVE

EX

EX
C

1-2 SHIFT VALVE

2120647.74
5/27/93

In Second Range, solenoids B, F and H are energized. Solenoids C, D and J are not energized.
As the transmission shifts into second range, solenoid B is energized. This directs main pressure to the top of the
1-2 shift valve, forcing it down. This exhausts the first-clutch apply circuit and allows main pressure into the
second-clutch apply circuit. Forward-clutch remains applied, and since second clutch is now applied, the
transmission shifts into second range.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
THIRD RANGE FLUID FLOW (ON-HIGHWAY)

MAIN
FORWARD
REVERSE
VALVE

NEUTRAL
RANGE VALVE

MAIN

EX

EX

EX

EX

FWD.
CLUTCH

EX

FOURTH
CLUTCH

EX

EX

EX

EX

EX

SECOND
CLUTCH

EX

THIRD
CLUTCH

B
EX

FIRST
CLUTCH

EX

EX

EX

EX

2-3 SHIFT VALVE

EX

EX
C

1-2 SHIFT VALVE

2120647.75
5/27/92

In Third Range, solenoids B, C, F and H are energized. Solenoids D and J are not energized.
In third range, solenoid C becomes energized. This directs main pressure to the top of the 2-3 shift valve, forcing
it down. This exhausts the second-clutch apply circuit and allows main pressure into the third-clutch apply
circuit. Forward clutch remains applied, and since third clutch is now applied, the transmission shifts into
third range.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
FOURTH RANGE FLUID FLOW (ON-HIGHWAY)
MAIN
3-4
SHIFT
VALVE

EX

FORWARD
REVERSE
VALVE

NEUTRAL
RANGE VALVE

MAIN

EX

EX

EX

EX

THIRD
CLUTCH

EX

FWD.
CLUTCH

FOURTH
CLUTCH

EX

EX

EX

EX

EX

EX

EX

SECOND
CLUTCH
B
EX

FIRST
CLUTCH

EX

EX

EX

EX

2-3 SHIFT VALVE

EX

EX
C

1-2 SHIFT VALVE

2120647.76
5/27/93

In Fourth Range, solenoids B, C, D, F and H are energized. Solenoid J is not energized.

In fourth range, solenoid D becomes energized. This directs main pressure to the bottom of the 3-4 shift valve,
forcing it up. This exhausts the third-clutch apply circuit and allows main pressure into the fourth-clutch apply
circuit. Forward-clutch remains applied, and since fourth clutch is now applied, the transmission shifts into
fourth range.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
REVERSE FLUID FLOW (ON-HIGHWAY)
MAIN
FORWARD
REVERSE
VALVE

NEUTRAL
RANGE VALVE

MAIN

EX

EX

EX

EX

FWD.
CLUTCH

EX

FOURTH
CLUTCH

EX

EX

EX

EX

SECOND
CLUTCH

EX

EX

THIRD
CLUTCH

B
EX

FIRST
CLUTCH

EX

EX

EX

EX

2-3 SHIFT VALVE

EX

EX
C

1-2 SHIFT VALVE

2120647.77
5/27/93

In Reverse, only solenoid H is energized. All other solenoids are not energized.
The shift to reverse begins with the transmission in Neutral. In Neutral, J is the only energized solenoid. It directs
main pressure to the top of the neutral range valve, which, along with spring pressure, keeps the neutral range
valve positioned down. This causes main pressure to deadhead at the neutral range valve. Main pressure
cascading through the 2-3 shift valve and the 1-2 shift valve keeps first clutch applied. Since only first clutch is
applied, the transmission is in Neutral.
When Reverse is selected, solenoid J is de-energized and solenoid H is energized. Solenoid J exhausts pressure
on top of the neutral range valve, and solenoid H directs main pressure to the bottom of the neutral range valve,
positioning it up against spring pressure. This allows main pressure to flow through the neutral range valve to the
forward/reverse valve, which is positioned down. Main pressure flows through the forward/reverse valve into the
fourth-clutch apply circuit. Since first clutch and fourth clutch are applied, the transmission shifts into Reverse.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
TRIMMER REGULATOR VALVE OPERATION (ON-HIGHWAY)

TRIMMER
REGULATOR
VALVE

TRIMMER
REGULATOR
VALVE

EX

EX

E
SOLENOID

EX

MAIN

EX

MAIN

MAIN

MAIN

EX

EX

TO TRIMMER

E
SOLENOID

TO TRIMMER
2120647.78
12/11/92

During forward operation, the ECU may energize or de-energize solenoid E. When solenoid E is de-energized,
the trimmer regulator valve is moved down by spring force. This allows oil pressure to flow through the trimmer
regulator to the bottom of the trimmer valves. This pressure works with the trimmer spring to create higher initial
clutch-apply pressure and firm shifts.
When solenoid E is energized, the trimmer regulator valve is lifted up against spring force, blocking the flow of
oil pressure through the trimmer regulator to the bottom of the trimmers. This lowers the initial clutch-apply
pressure, resulting in smoother shifts.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
LOCKUP CLUTCH APPLICATION (ON-HIGHWAY)

LOCK-UP
RELAY
VALVE

LOCK-UP
RELAY
VALVE

G
SOLENOID

EX

LOCK
UP

EX
EX

MAIN

EX

LOCK
UP

MAIN
CONVERTER
CIRCUIT

CONVERTER
CIRCUIT

MAIN

G
SOLENOID

MAIN

2120647.79
5/27/93

When the ECU senses the appropriate conditions, it can initiate lockup by energizing solenoid G. When solenoid
G is energized, it directs main pressure to the top of the lockup relay valve. This positions the valve down,
allowing main pressure to enter the lockup-clutch apply circuit.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
ELECTRICAL FAILURE (ON-HIGHWAY)
MAIN
FORWARD
REVERSE
VALVE

NEUTRAL
RANGE VALVE

MAIN

EX

EX

EX

EX

FWD.
CLUTCH

EX

FOURTH
CLUTCH

EX

EX

EX

EX

EX

SECOND
CLUTCH

EX

THIRD
CLUTCH

B
EX

FIRST
CLUTCH

EX

EX

EX

EX

2-3 SHIFT VALVE

EX

EX
C

1-2 SHIFT VALVE

2120647.80
12/11/92

The systems latching and non-latching solenoid configuration provides transmission operation during electrical
failure. When electrical failure occurs, all latching solenoids stay in position. This locks the transmission in
range, inhibiting all shifts.
Non-latching solenoids become immediately de-energized, exhausting main pressure. Solenoid G exhausts the
lockup clutch. Solenoid E no longer directs main pressure to the trimmer regulator valve, allowing the valve to
move down. De-energizing solenoid H stops the flow of main pressure to the bottom of the neutral range valve.
But since the valve upper land area is larger, main pressure keeps the valve positioned up, allowing pressure to
continue flowing to the forward/reverse valve.
As long as the engine continues running, the neutral range valve stays up and the latching solenoids keep their
corresponding valves in position. Once the engine is stopped and main pressure flow ceases, the neutral range
valve moves down due to spring pressure, exhausting the main pressure flowing to the forward/reverse valve. If
electrical failure still exists upon re-start, the previously-energized latching solenoids continue to direct pressure,
but the forward clutch is no longer applied, resulting in Neutral.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
TYPICAL FLUID FLOWS - OFF-HIGHWAY OVERVIEW
Component Description and Configuration
The off-highway Electronically-Controlled valve body relies on solenoids to control fluid flow throughout the
transmission. The valve body configuration is similar to Shift Pattern Generator (SPG) units. A solenoid pressure
regulator valve creates solenoid pressure and directs it to a series of shift valves. Each shift valve has a
corresponding, non-latching solenoid. Solenoid B controls reverse shift valve position, solenoid C controls the
first-and-second shift valve, solenoid D controls the third-and-fourth shift valve, solenoid E controls the
fifth-and-sixth shift valve, and solenoid F controls the splitter shift valve. When a solenoid is de-energized,
solenoid pressure is directed to the top of the shift valve, forcing it down. Energizing a shift valve solenoid opens
an exhaust passage, allowing solenoid pressure to exhaust and spring force to move the shift valve up.
Main pressure from the priority valve cascades through the shift valves. Depending on shift valve position, main
pressure is either directed into a clutch-apply circuit, or the clutch-apply circuit is exhausted. Trimmer valves may
be located in clutch-apply circuits to regulate oncoming clutch application.
Two additional non-latching solenoids are located under the first-and-second shift valve and the splitter shift
valve. Solenoid A, when energized, exhausts first-and-second clutch-apply circuit pressure under the first-andsecond shift valve. And solenoid G, when energized, exhausts splitter-direct clutch-apply circuit pressure
under the splitter shift valve. These two solenoids are critical to lock-in-range during electrical failure
(discussed later).
NOTE:

The following fluid flow description is based on a CLBT 6062 transmission, a typical, six-speed,
off-highway electronically-controlled transmission. Although some components vary slightly
between models, the same operating principles apply.

DE-ENERGIZED

ENERGIZED
SOLENOID
PRESSURE

CLUTCH
APPLY
CIRCUIT

CLUTCH
APPLY
CIRCUIT

EX

TO NEXT
SHIFT
VALVE

SOLENOID
PRESSURE

EX

MAIN

EX

TO NEXT
SHIFT
VALVE

EX

MAIN

EX

EX

EX

EX

EX

EX

MAIN

SHIFT VALVE

MAIN

SHIFT VALVE

COPYRIGHT 1994 GENERAL MOTORS CORP.

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12/11/92

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
NEUTRAL FLUID FLOW (OFF-HIGHWAY)

3-4
SHIFT
VALVE

1-2
SHIFT
VALVE
C

EX

SOLENOID
PRESSURE

5-6
SHIFT
VALVE

SPLITTER
SHIFT
VALVE
F

EX

EX

EX

TO REVERSE
SHIFT VALVE

EX

SPLITTER

OVERDRIVE

EX

EX

EX

EX

EX

EX

EX
EX

A
G

1-2
CLUTCH

3-4
CLUTCH

5-6
CLUTCH
MAIN

SPLITTER
DIRECT
2120647.82
12/11/92

In Neutral, solenoids A and F are energized. Solenoid A is not used in models with Lock-To-Neutral.
In neutral, solenoids A and F are energized. Solenoid F exhausts solenoid pressure above the splitter shift valve
and solenoid A ensures any clutch-apply pressure under the first-and-second shift valve is exhausted. The splitter
shift valve is moved up by spring force, allowing main pressure to enter the splitter-direct clutch-apply circuit.
Since splitter-direct is the only clutch applied, the transmission is in Neutral.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
FIRST RANGE FLUID FLOW (OFF-HIGHWAY)

3-4
SHIFT
VALVE

1-2
SHIFT
VALVE
C

EX

SOLENOID
PRESSURE

5-6
SHIFT
VALVE

SPLITTER
SHIFT
VALVE
F

EX

EX

EX

TO REVERSE
SHIFT VALVE

EX

SPLITTER

OVERDRIVE

EX

EX

EX

EX

EX

EX

EX
EX

A
G

1-2
CLUTCH

3-4
CLUTCH

5-6
CLUTCH
MAIN

SPLITTER
DIRECT
2120647.83
5 /27/93

In First Range, solenoids C and F are energized.

As the transmission shifts into first, solenoid F remains energized, solenoid A is de-energized and solenoid C
becomes energized. Solenoid C exhaust passage opens, allowing the first-and-second shift valve to move up. This
allows main pressure into the first-and-second clutch-apply circuit. Clutch-apply pressure is also directed to the
bottom of the first-and-second shift valve. Since the splitter-direct clutch and first-and-second clutch are applied,
the transmission shifts into first range.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
SECOND RANGE FLUID FLOW (OFF-HIGHWAY)

3-4
SHIFT
VALVE

1-2
SHIFT
VALVE
C

EX

SOLENOID
PRESSURE

5-6
SHIFT
VALVE

SPLITTER
SHIFT
VALVE
F

EX

EX

EX

TO REVERSE
SHIFT VALVE

EX

SPLITTER

OVERDRIVE

EX

EX

EX

EX

EX

EX

EX
EX

A
G

1-2
CLUTCH

3-4
CLUTCH

5-6
CLUTCH
MAIN

SPLITTER
DIRECT
2120647.84
5/27/92

In Second Range, solenoids C and G are energized. Solenoid G is not used in models
with Lock-To-Neutral
In second range, solenoid F is de-energized, solenoid G is energized, and solenoid C remains energized. The
first-and-second shift valve continues to direct main pressure into the first-and-second clutch apply circuit.
Solenoid G exhausts splitter-direct clutch-apply pressure under the splitter-direct shift valve, allowing the valve
to move down (solenoid F is no longer energized). This directs main pressure into the splitter-overdrive clutchapply circuit. Since the splitter-overdrive clutch and the first-and-second clutch are applied, the transmission
shifts into second range.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
THIRD RANGE FLUID FLOW (OFF-HIGHWAY)

3-4
SHIFT
VALVE

1-2
SHIFT
VALVE
C

EX

SOLENOID
PRESSURE

5-6
SHIFT
VALVE

SPLITTER
SHIFT
VALVE
F

EX

EX

EX

TO REVERSE
SHIFT VALVE

EX

SPLITTER

OVERDRIVE

EX

EX

EX

EX

EX

EX

EX
EX

A
G

1-2
CLUTCH

3-4
CLUTCH

5-6
CLUTCH
MAIN

SPLITTER
DIRECT
2120647.85
5/27/93

In Third Range, solenoids D and F are energized.

As the transmission shifts into third range, solenoids C and G are de-energized. The first-and-second shift valve is
moved down against spring force, and solenoid G blocks the splitter-direct exhaust passage under the splitter shift
valve. Solenoids D and F become energized. The splitter shift valve moves up, allowing main pressure into the
splitter-direct clutch-apply circuit. The third-and-fourth shift valve moves up, allowing main pressure into the
third-and-fourth clutch-apply circuit. This results in third range.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
FOURTH RANGE FLUID FLOW (OFF-HIGHWAY)

3-4
SHIFT
VALVE

1-2
SHIFT
VALVE
C

EX

SOLENOID
PRESSURE

5-6
SHIFT
VALVE

SPLITTER
SHIFT
VALVE
F

EX

EX

EX

TO REVERSE
SHIFT VALVE

EX

SPLITTER

OVERDRIVE

EX

EX

EX

EX

EX

EX

EX
EX

A
G

1-2
CLUTCH

3-4
CLUTCH

5-6
CLUTCH
MAIN

SPLITTER
DIRECT
2120647.86
5/27/93

In Fourth Range, solenoids D and G are energized. Solenoid G is not used in models
with Lock-To-Neutral.
In fourth range, solenoid D remains energized, keeping the third-and-fourth shift valve up and the third-andfourth clutch applied. Solenoid G becomes energized, exhausting splitter-direct clutch-apply pressure under the
splitter shift valve. Since solenoid F is now de-energized, the splitter shift valve moves down, allowing main
pressure into the splitter-overdrive clutch-apply circuit. This results in fourth range.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
FIFTH RANGE FLUID FLOW (OFF-HIGHWAY)

3-4
SHIFT
VALVE

1-2
SHIFT
VALVE
C

EX

SOLENOID
PRESSURE

5-6
SHIFT
VALVE

SPLITTER
SHIFT
VALVE
F

EX

EX

EX

TO REVERSE
SHIFT VALVE

EX

SPLITTER

OVERDRIVE

EX

EX

EX

EX

EX

EX

EX
EX

A
G

1-2
CLUTCH

3-4
CLUTCH

5-6
CLUTCH
MAIN

SPLITTER
DIRECT
2120647.87
5/27/93

In Fifth Range, solenoids E and F are energized.

As the transmission shifts into fifth range, solenoids D and G are de-energized and solenoids E and F are
energized. Solenoid E opens the exhaust passage above the fifth-and-sixth shift valve, allowing the valve to move
up, directing main pressure into the fifth-and-sixth clutch-apply circuit. Solenoid G blocks the splitter-direct
clutch-apply circuit exhaust under the splitter shift valve, and solenoid F exhausts solenoid pressure above the
splitter shift valve. This positions the splitter shift valve up, allowing main pressure into the splitter-direct clutchapply circuit. Since the fifth-and-sixth clutch and splitter-direct clutch are applied, the transmission shifts into
fifth range.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
SIXTH RANGE FLUID FLOW (OFF-HIGHWAY)

3-4
SHIFT
VALVE

1-2
SHIFT
VALVE
C

EX

SOLENOID
PRESSURE

5-6
SHIFT
VALVE

SPLITTER
SHIFT
VALVE
F

EX

EX

EX

TO REVERSE
SHIFT VALVE

EX

SPLITTER

OVERDRIVE

EX

EX

EX

EX

EX

EX

EX
EX

A
G

1-2
CLUTCH

3-4
CLUTCH

5-6
CLUTCH
MAIN

SPLITTER
DIRECT
2120647.88
5/27/93

In Sixth Range, solenoids E and G are energized. Solenoid G is not used in models
with Lock-To-Neutral
In sixth range, solenoid E remains energized, keeping the fifth-and-sixth clutch applied. Solenoid G becomes
energized, exhausting splitter-direct clutch-apply pressure under the splitter shift valve. Since solenoid F is now
de-energized, the splitter shift valve moves down, allowing main pressure into the splitter-overdrive clutch-apply
circuit. This results in sixth range.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
REVERSE FLUID FLOW (OFF-HIGHWAY)
SPLITTER
SHIFT
VALVE

SOLENOID
PRESSURE

EX

EX

REV.
CLUTCH
SPLITTER

OVERDRIVE

EX

EX

REVERSE
SHIFT
VALVE

EX

MAIN

SPLITTER
DIRECT

2120647.89
12/11/92

In Reverse, solenoids A, B and F are energized. Solenoid A is not used in models

with Lock-To-Neutral.
The shift to Reverse begins with the transmission in neutral. Solenoids A and F are energized, positioning the
splitter shift valve up, allowing main pressure into the splitter-direct clutch-apply circuit. When reverse is
selected, solenoid B becomes energized. This exhausts solenoid pressure above the reverse shift valve,
positioning the valve up, allowing main pressure into the reverse clutch-apply circuit. Since splitter-direct clutch
and reverse clutch are applied, the transmission shifts into Reverse.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
LOCKUP CLUTCH APPLICATION (OFF-HIGHWAY)

TORQUE
CONVERTER

TORQUE
CONVERTER

DE-ENERGIZED

ENERGIZED

LOCKUP
SHIFT
VALVE

LOCKUP
SHIFT
VALVE

EX

EX

EX

EX

K
MAIN

MAIN
2120647.90
12/11/92

When the ECU senses the appropriate conditions, it can initiate lockup by energizing solenoid K. When solenoid
K is energized, it exhausts main pressure under the lockup shift valve. The shift valve moves down, allowing
main pressure from the priority valve to enter the lockup clutch-apply circuit. This eliminates the need for pitot
pressure in conventional valve bodies.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

OPERATIONAL OVERVIEW
ELECTRICAL FAILURE (OFF-HIGHWAY)

ENERGIZED

DE-ENERGIZED
SOLENOID
PRESSURE

SOLENOID
PRESSURE
CLUTCH
APPLY
CIRCUIT

CLUTCH
APPLY
CIRCUIT

EX

TO NEXT
SHIFT
VALVE

EX

MAIN

EX

TO NEXT
SHIFT
VALVE

EX

MAIN
EX

EX
EX

EX

EX

EX

MAIN

MAIN

SHIFT VALVE

SHIFT VALVE
2120647.91
5/27/93

The system design allows it to lock-in-range during electrical failure. Whenever a shift valve is positioned up,
clutch apply or cascading main pressure is directed to the bottom of the shift valve. During electrical failure, all
solenoids are de-energized, but the constant flow of pressure under the shift valve keeps it positioned up. All
shifts are blocked, but applied clutches remain applied as long as the engine is running. Once the engine is shut
down, pressure is no longer directed to the bottom of shift valves previously positioned up. If the electrical failure
still exists after the engine is re-started, none of the solenoids are energized and all shift valves are forced down
by solenoid pressure. This results in neutral, with only the splitter-overdrive clutch applied.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

COMPONENT INSTALLATION AND ADJUSTMENT
INTRODUCTION
Proper Electronic Control component installation and adjustment is critical to proper system performance.
Though applications vary, the following guidelines must be followed for proper system operation.

ELECTRONIC CONTROL UNIT (ECU)

Mount the ECU in an area protected from direct exposure to weather, road hazards, cleaning sprays and high
concentrations of dust and sunlight.
Mount the unit in an area free from road splash. Do not allow the ECU to be immersed in water.
Mount the ECU in the coolest practical location with good ventilation. Avoid exposing the ECU to
temperature extremes.

Maximum continuous
Maximum startup
Maximum intermittent (up to 1 hr.)
Minimum exposure

Operational

Non-Operational

55C (130F)
71C (160F)

-40C (-40F)

85C (185F)

105C (220F)
-54C (-65F)

ECU Temperature Limits

Do not mount the ECU to the vehicles power package (transmission, engine or driveline). Bolt the ECU securely
to the vehicles cab or chassis.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

COMPONENT INSTALLATION AND ADJUSTMENT
ELECTRONIC CONTROL UNIT (ECU)
Position the connectors down to prevent water from entering the connectors or ECU. If the connectors cant be
positioned down, they may be placed at either 3 or 9 oclock. Never position the connectors up.
J3
J1
A

J1
B

J1
A
J1

J3

J1
J3

J1

9 O'CLOCK OR 3 O'CLOCK
ACCEPTABLE

PREFERRED

UNACCEPTABLE
2120647.02
12/9/92

ECU Mounting Orientation

Mount the ECU in a location that minimizes operator and service personnel contact. Leave enough clearance
(at least 8 inches) to allow connector removal without having to remove the ECU. Allow room for slack in the
harnesses; this reduces stress on the harnesses and connectors.
Mount the ECU as close to the power source as possible. Long battery power wires result in voltage drops. Keep
the power wires short to help the ECU meet voltage requirements. The ECUs main power and ground inputs
should be dedicated - no other electrical components should share the ECUs power and ground inputs. The
ECU requires a minimum of 10 volts for operation. 16 volts is the maximum continuous voltage the system
handles, and 19 volts is the maximum intermittent voltage the system can sustain.
In some applications, ECU power must be supplied by dual power sources (off-highway and emergency vehicle
applications, and vehicles equipped with Jacobs engine brakes). An engine or transmission oil pressure switch
and the master ignition switch should both supply ECU power. This assures that power is supplied to the ECU
under all operating conditions. (Detailed wiring information is located in the Vehicle Interface section of
this document.)
The ECU requires continuous power for storing diagnostic codes and throttle sensor calibration values. This
memory must be powered by 12 volts even when the engine is shut down and the ignition switch is off.
Without continuous memory, all diagnostic and throttle sensor information is lost; when power is restored, all
information necessary for operation is automatically regenerated by the ECU, but previously stored information
(trouble codes, throttle position, etc.) is lost.
The ECU is a sealed component and is not serviceable in the field. PROM removal and replacement is the only
field service performed on ECUs and should be done only by authorized Allison service outlets.

2-2

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

COMPONENT INSTALLATION AND ADJUSTMENT
PROGRAMMABLE READ ONLY MEMORY (PROM)

PROM
REMOVAL TOOL

2120647.03
12/15/92

PROM Removal and Installation

The Electronic Control PROM can be removed and replaced. The PROMs tangs are indexed, and though it is
difficult, it is possible to install the PROM incorrectly. Installing the PROM incorrectly will erase the stored
information and may also cause physical damage.

NARROW SLOT
NARROW
TAB

2120647.04
12/10/92

PROM Indexing
Make sure the PROM slides gently into place. If more than light resistance is encountered, check tang indexing
and alignment and gently re-insert the PROM. Forcing the PROM or installing it backwards results in damage.
Static electricity can also damage the PROM. Avoid touching the PROM legs with your fingers or placing the
PROM on static producing surfaces.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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;;;;
;;
; ;;
;;;
;;;
;;
;;

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

COMPONENT INSTALLATION AND ADJUSTMENT
OUTPUT SPEED SENSOR

On-highway output speed sensors fit into the transmission rear cover and are secured with a bolt. No adjustment
is required.

;
;;

;;

OUTPUT SPEED SENSOR

; ;
;
;;;
;;;
;
;

;;

2120647.05
12/10/92

Output Speed Sensor Located on Rear Cover of Transmission

Off-highway output speed sensors must be adjusted. Thread the sensor into the transmission housing until it
makes contact with one of the speed sensor gears teeth, then back it out 3/4 to 1 turn and secure it with the jam
nut. Make sure contact is made on the tip of the tooth and not between the teeth. Serious damage to the speed
sensor and speed sensor gear teeth could result from improper installation/adjustment.

CORRECT
INCORRECT

2120647.06
12/14/92

Off-Highway Output Speed Sensor Installation and Adjustment

The output speed sensor wiring is used for the speed sensor only. Do not connect any other devices to the output
speed sensor wiring, connector, or pick-up. Do not use this signal for an electric speedometer or tachograph.
Connecting other components to this circuit can cause improper shifting, diagnostic codes and damage.

2-4

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

COMPONENT INSTALLATION AND ADJUSTMENT
THROTTLE POSITION SENSOR (TPS)
Installation
The throttle position sensor can be mounted on the chassis or power package. When mounted on the power
package, an Allison-supplied isolator must be used. Provide a solid mount - avoid unsupported brackets or thin,
flexible mounting bases. Mount the sensor on a flat surface (within 0.030 in.) to avoid sensor housing distortion.
The sensor body should be mounted above the engine fuel control connection with its cable pointing down.
ENGINE MOUNTED
BRACKET
GUSSET
REQUIRED

ISOLATOR
ASSEMBLY

2120647.07
12/14/92

TPS Mounting Bracket

Add protective shrouding if the sensor is mounted in an area susceptible to operator or technician damage. Shield
the sensor and any of its components that are within 12 inches of turbochargers, exhaust manifolds, or other heat
sources. The sensor is designed to withstand no more than 250 degree (F) continuous temperatures and 300
degree (F) intermittent heat soaks.
The throttle position sensor must read actual fuel shaft movement, not throttle breakover movement. If the sensor
reads breakover movement, it sees the additional travel as fuel shaft movement and self-adjusts incorrectly. Be
sure that the breakover force is capable of overcoming the return force of the throttle sensor and all other
attached linkages.
FULL THROTTLE

CLOSED THROTTLE

OVERSTROKED

CLOSED THROTTLE

FULL THROTTLE

2120647.08
12/8/92

Throttle Breakover Movement

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

COMPONENT INSTALLATION AND ADJUSTMENT
THROTTLE POSITION SENSOR (TPS)
Installation (continued)
The throttle position sensor cable must be installed without excessive bends or angles. Do not exceed a 10 degree
maximum installed cable angle. Linkages should move freely without binding or sticking. Be sure the sensor
cable mounting wont interfere with throttle movement.
10.0 MAX INSTALLED
OPERATING ANGLE
IN ALL DIRECTIONS

LOADING
IN
TENSION
ONLY

BENDING LOAD
APPLIED

UNACCEPTABLE INSTALLATION

ACCEPTABLE INSTALLATION

2120647.09
12/8/92

Acceptable TPS Cable Angle

Adjustment
Although the throttle position sensor is self-adjusting, an initial adjustment must be performed whenever the
sensor is first installed or removed and reinstalled. Throttle sensor cables are available with slotted ends (standard
for earlier models) and hitch pin ends (later models). Adjustments are necessary when changing from one style to
the other.
Initial throttle position sensor adjustment should center the sensor between the error zones.
255 COUNTS

0 COUNTS

233 COUNTS

14 COUNTS

APPROX.
0.75 INCH
STROKE

ERROR
ZONE

IDLE
0

0.2 INCH

ERROR
ZONE

FULL
THROTTLE
1.8 INCHES

1.9 INCHES

APPROX.
0.5 INCH
FULLY
RETRACTED

FULLY
EXTENDED

Initial TPS Adjustment - Error Zones

2-6

COPYRIGHT 1994 GENERAL MOTORS CORP.

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12/8/92

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

COMPONENT INSTALLATION AND ADJUSTMENT
THROTTLE POSITION SENSOR (TPS)
Adjustment (continued)
Pull the cable 0.5 inch from the fully retracted position - this sets closed throttle position. Make sure that 0.625 to
0.9 inch working stroke exists. When properly adjusted, the throttle position sensor will still have travel left when
the throttle is wide open (the sensor should not be fully extended when the throttle is wide open). From fully
retracted to fully extended, the sensor will travel about 1.9 inches. Adjusting an initial 0.5 inch from fully
retracted will place the sensor in a safe range for most applications. No further adjustment is required unless the
sensor is replaced or linkage/cable problems occur.
ENGINE
FUEL CONTROL
SHAFT

MINIMUM 0.25 IN.

MAXIMUM 1.750 IN.

RECOMMENDED
WORKING STROKE
0.625 IN. TO 0.9 IN.
NOM 0.75 IN.

INTERNAL STOPS 1.9 IN.

2120647.11
5/19/93

Initial TPS Adjustment

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

COMPONENT INSTALLATION AND ADJUSTMENT
SHIFT SELECTORS
The Electronic Control uses two types of shift selectors - push button and lever. Sealed Plus II ECUs sometimes
use secondary shift selectors. Installation requirements for primary and secondary selectors are the same.

Push Button Shift Selector

The push button shift selector is designed for use in an enclosed cab, protected from direct contact with moisture,
high concentrations of dust and direct sunlight. Like the ECU, the shift selector must be protected from
temperature extremes.

Maximum continuous
Maximum startup
Maximum intermittent (up to 1 hr.)
Minimum exposure

Operational

Non-Operational

55C (130F)
71C (160F)

-40C (-40F)

85C (185F)

105C (220F)
-54C (-65F)

Shift Selector Temperature Limits

Mount the shifter in the vehicle cab using the four mounting holes on the top of the selector. Secure the selector
to a solid base or panel. Use fasteners that allow shift selector removal and reinstallation (cage nuts, threaded
mounting holes, etc.).

MOUNTING HOLES

DO

T
NO T
IF
SH

2120647.13
12/10/92

Mounting the Push Button Shift Selector

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

COMPONENT INSTALLATION AND ADJUSTMENT
SHIFT SELECTORS
Push Button Shift Selector
Mount the selector at a minimum 20-1/2 degree angle (longitudinally) from the vehicle horizontal axis. This is
necessary to keep liquid and dirt from accumulating on the shifter face. Mount the selector so that Range
Displays and the DO NOT SHIFT light are clearly visible to the operator.
VEHICLE LONGITUDINAL AXIS

DO

T
NO T
IF
SH

MINIMUM 20-1/2
DEGREE ANGLE

2120647.14
12/10/92

Mounting Angle for Push Button Shift Selector

The push button shift selector connector is not sealed. Mount the selector so that the connector and harness are
protected from moisture and dirt, as well as operator, technician, or passenger contact. Leave a minimum of
6 inches of slack in the harness to reduce stress on the harness and connector and allow for connector removal.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

COMPONENT INSTALLATION AND ADJUSTMENT
SHIFT SELECTORS
Lever Shift Selector
The lever shift selector and its connector are sealed. They can withstand moisture, but should not be immersed
in water.
The lever selector has two mounting provisions. Top mounting is similar to push button shift selectors. Remove
the selectors bezel, mount the selector with four fasteners, then reinstall the bezel.

MOUNTING HOLE

MOUNTING HOLE

2120647.15
12/18/92

Mounting the Lever Shift Selector

The lever selector can also be side mounted. The selector housing has four tapped holes (metric M6 X 1.00 - 6H)
that can be used for mounting the shifter to the side of a pedestal.

2-10

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

COMPONENT INSTALLATION AND ADJUSTMENT
WIRING HARNESSES
Allison provides wiring harnesses for properly connecting Electronic Control components. Harnesses not
supplied by Allison (if used) must be produced by a qualified harness manufacturer. Proper harness quality,
integrity, and configuration are essential to system performance.
The installer is responsible for warranty on any components not supplied by Allison. The installer is also
responsible for any damage to or claims against Allison Transmission Electronic Control components resulting
from the failure of components not supplied by Allison. Improper harness installation and connections can cause
false trouble codes and damage.

Protecting The Harness

All wiring harnesses must be carefully routed to avoid sharp bends, kinking, pinching, cutting, binding, rubbing,
and excessive pulling.
Protect the cable from road hazards, sharp surfaces, high temperatures, and corrosives by using tubes and
shielding (harnesses are designed to withstand no more than 250 degrees F/121 degrees C).
Use nylon ties (or similar tie wraps) to secure the harness to the vehicle. Coil any excess harness and secure it
with nylon ties, also.
When routing through sheet metal, insert rubber guards or grommets to prevent nicks or cuts to the harness. Do
not run screws through the harness when installing accessories.
NOTE:

The harness must be installed so that the connectors are not strained or stressed. Do not allow
the connectors to support the weight of the harness. Secure the harness using nylon ties or
appropriate strain reliefs.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

COMPONENT INSTALLATION AND ADJUSTMENT
WIRING HARNESSES
Harness Connectors
WARNING: Always disconnect the Electronic Control wiring harnesses before arc welding on the vehicle.
Never jump start the vehicle using arc welding equipment.

The Diagnostic Data Link (DDL) connector is part of the cab wiring harness. Mount the DDL connector in the
cab where it can be easily accessed by technicians, but out of the way of the operator and passengers.
Output speed sensor and throttle position sensor harness connectors are installed by pushing the connector into
the sensor body until a click is heard.
The main transmission connector plugs into the electrical bulkhead in the transmission housing. The connector is
indexed so it can only be installed one way. Once the harness connector pins are seated in the bulkhead connector,
the connector outer locking collar must be rotated. This secures the harness connector to the transmission
bulkhead connector.
ECU connectors are indexed for proper orientation. Carefully insert the connectors into the ECU. Once the
connectors are seated, torque the center locking screw to 7-13 inch pounds. Lever shift selector connectors are
installed using the same procedures. Avoid excessive pushing or bending when tightening the center screw
on any connector.
Push button shift selector connectors are indexed for proper installation. Carefully insert the connector into the
back of the selector, index the connector, then thread the connector locking collar onto the selector housing.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
INTRODUCTION
The term vehicle interface describes the electrical connections between the vehicle and the Electronic Control.
These connections are made through the cab and secondary mode wiring harnesses and supply power, ground and
option input/output signals to the ECU.
Interface connections can be either mandatory or optional. Mandatory interface connections are required for
every application. Optional connections are signal input and output wires that are connected when specific
options exist in the PROM.
This document provides isolated schematics that focus on each specific interface item, plus detailed operational
descriptions of each option. You will also find additional wiring information and suggestions that will guide you
through each interface connection.

ELECTRONIC CONTROL INQUIRY SYSTEM (ECIS)

The Electronic Control Inquiry System (ECIS) is an on-line data system that indicates which options are
programmed in a particular PROM. ECIS is updated daily and is available through all Distributor Parts
Departments. The system provides detailed PROM programming information, upshift points and downshift
points for primary mode and, if applicable, secondary mode operation.
The ECIS Users Manual provides step-by-step accessing information. It also contains a glossary with pertinent
explanations and definitions. Use ECIS and the Users Manual to determine which options are programmed and
how they should operate.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
MANDATORY VEHICLE INTERFACE
Connections Required For Basic Vehicle Operation
The following wiring connections are required for Electronically Controlled transmissions to operate.
Use 18 AWG minimum wire except where noted.
Always use good quality relays, connectors, and fasteners.
When discussing relays, the activation circuit controls the relay and the power circuit is the circuit
switched on and off by the relay.
Potentially high load junction points (bus bars, power strips, etc.) must be properly fused and fed by an
appropriately sized wire (16 AWG or bigger, depending on the load).

POWER CIRCUIT
FROM
POWER
SOURCE

POWER CIRCUIT

ARMATURE
TO LOAD

FROM
POWER
SOURCE

ARMATURE
TO LOAD

COIL
ACTIVATION
CIRCUIT

ACTIVATION
CIRCUIT
CONTACT

COIL
AT REST
(NO CURRENT FLOW)

NORMALLY
ACTIVATED
OPEN
(CONTACTS
CLOSE,
CONTACT
CURRENT FLOWS)

2120647.17
12/11/92

Relay Activation and Power Circuits

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COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
MANDATORY VEHICLE INTERFACE
EMI Shielding Ground - Wire 201

2K
WIRE 201

ECU

VEHICLE FRAME
NEAR ECU
2120647.18
12/8/92

Wire 201 is the ECU electromagnetic shielding ground. Ground this wire to the vehicle chassis to
minimize operational problems (improper shifting, false diagnostic codes, etc.) caused by electromagnetic
interference (EMI).
Ground wire 201 directly to a metal, non-painted portion of the chassis.
Do not change the wire length.
Do not connect wire 201 to battery ground or any other ground wires.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
MANDATORY VEHICLE INTERFACE
ECU Power - Wires 202A, 223A
Wires 202A and 223A provide positive power for the ECU.
The Electronic Control requires at least 10 volts for operation.
The system is designed to handle 16 volts continuously and up to 19 volts intermittently.
Wires 202A and 223A can be connected using one of the following options.
Option 1
CAUTION: Connecting wire 215 directly to power causes damage to ECU.

CHECK
TRANS

3H
215
202A
223A
208
209

2A
2B
1A
1B

ECU

OIL PRESS*

+IGN

12 BATTERY
VOLTAGE
OR 24 VOLTS

8A

*Oil pressure switch is only

required for emergency and
off-highway vehicle applications.

12 VOLTS FROM
BATTERY OR
VOLTAGE CONVERTER

DIRECT TO
BATTERY
GROUND

2120647.19
5/19/93

Using Option 1, a wire connected directly to the battery is routed through an 8-amp fuse to the power circuit of
two relays.
Positive voltage directly from the battery or voltage converter must be routed to each relay power circuit
through an 8-amp fuse.
The oil pressure switch can be either a transmission oil pressure switch or an engine oil pressure switch.
Regardless of switch type, it must remain closed whenever the engine is running.
Voltage coming out of the oil pressure switch can also be directed to the Check Transmission light relay
activation circuit (if used).
The single wire running to wires 202A and 223A must always be at least 12 AWG up to the
junction point.
Dual power is required on emergency vehicles and off-highway vehicles.
Wires 202A and 223A can be connected to buss bars as long as the buss bars are dedicated to the electronic
control system and are in close proximity to the battery.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
MANDATORY VEHICLE INTERFACE
ECU Power - Wires 202A, 223A
Option 2
CAUTION: Connecting wire 215 directly to power causes damage to ECU.

CHECK
TRANS

215

OIL
PRESSURE
SWITCH*

DIODE

202A
223A
208
209

3H

2A
2B
1A
1B

IGNITION/MASTER
SWITCH

ECU

8 AMP
*Oil pressure switch is only
required for emergency and
off-highway vehicle applications.

12 VOLTS FROM
BATTERY OR
VOLTAGE CONVERTER
12 BATTERY VOLTAGE
OR 24 VOLTS

DIRECT TO
BATTERY GROUND
2120647.20
5/19/93

Using Option 2, positive voltage directly from the battery or voltage converter is routed through an 8-amp fuse to
the power circuit of one relay.
The diode must be capable of handling full circuit current and voltage when the vehicle master ignition
switch is open.
The relay can be deleted if the master switch shown is dedicated to ECU wires 202A/223A only (no other
circuits can be connected to the switch contacts). When the relay is deleted, the switch must be capable of
handling ECU current draw (approximately 6 amps).
The oil pressure switch can be either a transmission oil pressure switch or an engine oil pressure switch.
Regardless of switch type, it must remain closed whenever the engine is running.
Voltage coming out of the oil pressure switch can also be directed to the Check Transmission light relay
activation circuit (if used).
The single wire running to wires 202A and 223A must always be at least 12 AWG up to the
junction point.
Wires 202A and 223A can be connected to buss bars as long as the buss bars are dedicated to the electronic
control system and are in close proximity to the battery.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
MANDATORY VEHICLE INTERFACE
ECU Continuous Power Memory - Wire 203

3A
WIRE 203
5A

ECU
MEMORY

12 VOLTS FROM BATTERY

OR VOLTAGE CONVERTER

2120647.21
12/8/92

Wire 203 supplies continuous power to the ECUs memory for storing diagnostic codes and throttle position
sensor calibration values.
Wire 203 must be connected directly to the positive terminal of the battery or voltage converter through a
5-amp fuse.
If wire 203 loses power, all historic diagnostic and throttle sensor calibration information will be lost.
Calibration information is regenerated when the vehicle is restarted, but previous diagnostic information
remains lost.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
MANDATORY VEHICLE INTERFACE
ECU Ground - Wires 208, 209

NEGATIVE
BATTERY
TERMINAL

12 GA
WIRE

18 GA
WIRE

WIRE 209

1B

WIRE 208

1A

ECU

2120647.22
12/8/92

Wires 208 and 209 are connected directly to the battery negative terminal and provide ECU ground.
A single wire should be run directly from the battery negative terminal to wires 208 and 209.
The single wire running to wires 208 and 209 must always be at least 12 AWG up to the junction point.
Do not ground wires 208 and 209 to the vehicle chassis.
Wires 208 and 209 can be connected to buss bars as long as the buss bars are dedicated to the electronic
control system and are in close proximity to the battery.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
MANDATORY VEHICLE INTERFACE
Reverse Signal - Wire 214
CAUTION: Connecting wire 214 directly to power causes damage to ECU.

REVERSE SIGNAL
CIRCUIT IN VEHICLE
2D

ECU

WIRE 214
0.4 AMP MAX
+ 12 OR
+ 24 VOLTS

WIRE 214 IS GROUNDED

WHEN IN REVERSE

2120647.23
12/8/92

Wire 214 provides a negative (ground) signal whenever the transmission is in reverse.
When the transmission is in reverse, wire 214 goes from open to ground.
This provides an activation circuit signal to an OEM-supplied relay. This relay controls the vehicle reverse
warning device.

3-8

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
MANDATORY VEHICLE INTERFACE
Shift Selector Power - Wire 225 or 235

MASTER/
IGNITION
SWITCH
WIRE 225

12

+ 12 VOLTS

PUSH
BUTTON
SHIFT
SELECTOR

MASTER/
IGNITION
SWITCH
WIRE 235

OR

15

+ 24 VOLTS

PUSH
BUTTON
SHIFT
SELECTOR

2120647.25
12/8/92

Shift selector power is supplied using either wire 225 or wire 235.
Use wire 225 for 12-volt systems (lever and push button selectors).
Use wire 235 for 24-volt systems (lever and push button selectors).

MASTER/
IGNITION
SWITCH
WIRE 225
+ 12 VOLTS

1C

LEVER
SHIFT
SELECTOR

MASTER/
IGNITION
SWITCH
OR

WIRE 235
+ 24 VOLTS

2A

LEVER
SHIFT
SELECTOR

2120647.26
12/8/92

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
MANDATORY VEHICLE INTERFACE
Selector Lamp Circuit - Wires 230, 233 and 234
12-VOLT SYSTEMS
GROUND

DASH CONTROL

GROUND

230 10

24-VOLT SYSTEMS
DASH CONTROL

233 13

NOT USED

234 14

GROUND

230 10

233

13

234 14

PUSH BUTTON
SHIFT SELECTOR

PUSH BUTTON
SHIFT SELECTOR

2120647.27
12/8/92

The shift selector has two 12-volt, one watt lamps which are controlled by the vehicle dash-dimmer rheostat.
Wire 234 (ground for 12- and 24-volt circuits) should be connected to vehicle ground at the earliest
convenient point.
On 12-volt systems, wire 230 is grounded and positive voltage is supplied from the dashboard illumination
control through wire 233.
On 24-volt systems, wire 233 is not used and positive voltage from the dashboard illumination control is
supplied through wire 230.

12-VOLT SYSTEMS
GROUND

DASH CONTROL

GROUND

230 1F

24-VOLT SYSTEMS
DASH CONTROL

233 2F
234 3F
LEVER SHIFT SELECTOR

NOT USED

GROUND

230 1F
233 2F
234 3F
LEVER SHIFT SELECTOR
2120647.28
12/8/92

3-10

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
MANDATORY VEHICLE INTERFACE
Neutral Start - Wire 231
CAUTION: Connecting wire 231 directly to power causes damage to ECU.

NEUTRAL SIGNAL
CIRCUIT IN VEHICLE
9

PUSH
BUTTON
SHIFT
SELECTOR

WIRE 231
0.5 AMP MAX
+ 12 OR
+ 24 VOLTS

WIRE 231 IS GROUNDED

WHEN IN NEUTRAL

NEUTRAL SIGNAL
CIRCUIT IN VEHICLE
1A

LEVER
SHIFT
SELECTOR

WIRE 231
0.5 AMP MAX
+ 12 OR
+ 24 VOLTS

WIRE 231 IS GROUNDED

WHEN IN NEUTRAL
2120647.29
12/9/92

When the vehicle master switch is turned on and the shift selector is in neutral, wire 231 is grounded. This ground
signal is used with an OEM-supplied relay to control the vehicles neutral start circuit.
When the selector is in neutral and the vehicle master switch is on, wire 231 provides a ground to the
neutral start relay activation circuit.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Optional cab harness interface connections are wired through the cab wiring harness (200 series wires). Options
must be programmed and properly wired to operate. Simply wiring the option will not enable it - the option must
be programmed. If necessary, determine PROM characteristics using ECIS.

Electronic Speedometer Output - Wire 205

CAUTION: Connecting wire 205 to power causes damage to the ECU.

3G

ECU

WIRE 205

SPEEDOMETER

SPEEDOMETER SIGNAL

TRANSMISSION
OUTPUT SPEED
SENSOR

VOLTS DC

(NON-ZERO CROSS-REFERENCING SIGNAL)

VARIATION DEPENDS ON LOAD

3.5

0.5
0

2120647.30
5/19/93

Wire 205 is an output that provides a pulse signal from the ECU for electronic speedometers, odometers or
tachs to use.
Connecting wire 205 to positive voltage can damage the ECU.
Do not connect electronic speedometers, tachs, etc. to the speed sensor circuit.
Wire 205 provides a square wave, non-zero crossing signal which varies from 0 to +5 volts. Pulse
frequency varies, depending on transmission model.
On highway - 16 pulses per output shaft revolution.
Off-highway 5000 and 6000 series - 39 pulses per output shaft revolution.
Off-highway 8000 and 9000 series - 41 pulses per output shaft revolution.
Wire 205 can support up to two low-power loads (high impedance). If more than two devices need to be
installed, contact Allison Transmission Engineering.

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COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Retarder Enable and Output - Wires 211 and 213
CAUTION: Connecting wire 213 directly to power causes damage to the ECU.

DISABLE
SWITCH

ENABLE
SWITCH

+ 12 OR
+ 24 VOLTS
ACCESSIBLE TO
OPERATOR TO
DISABLE
RETARDER
CIRCUIT

3F
WIRE 211

ACTIVATED BY
VEHICLE SYSTEM
SUCH AS
RETARDER
CONTROL

THROTTLE POSITION
OUTPUT SPEED
LOCKUP MODE

TO
VEHICLE
SYSTEM

ECU 3D

WIRE 213
0.4 AMP MAX

+ 12 OR
+ 24 VOLTS
WIRE 213 IS GROUNDED
WHEN ALL CONDITIONS
ARE MET
2120647.31
5/19/93

When the ECU detects power on wire 211, it recognizes that the operator has requested retarder or compression
brake operation.
If programmed conditions are correct, wire 213 goes from open to ground, applying the compression brake
or retarder.
Wire 211 is an input for retarder enable. When the ECU recognizes positive voltage on wire 211, it
recognizes a request for retarder or compression brake application.
Wire 213 is an output for retarder apply. When the ECU recognizes retarder or compression brake request
(through wire 211), it checks the condition of certain items. When the ECU senses the appropriate
conditions, wire 213 (which is directed to the retarder/compression brake relay activation circuit) goes from
open to ground.

COPYRIGHT 1994 GENERAL MOTORS CORP.

3-13

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Retarder Enable and Output - Wires 211 and 213
Retarder Options
Retarder options indicate the type of signals the ECU must receive before the retarder will apply. There are four
retarder options.
Option 1
Option 1 lets the retarder apply when requested, without checking any other conditions.
When wire 211 is connected to positive voltage, the ECU grounds wire 213, enabling the retarder.
This option is used primarily in off-highway applications.
Option 3
Option 3 (there is no Option 2) lets the retarder apply once all of the following conditions are met:
Wire 211 is connected to positive voltage.
The throttle position is near zero (fully closed).
The transmission output speed is above a programmed value.
The lock-up clutch is applied.
When these conditions are met, the ECU grounds wire 213. This option is used primarily with engine
brake applications.
Option 4
Option 4 applies the retarder when the following conditions are met:
Wire 211 is connected to positive voltage.
The throttle position is near zero (fully closed).
When these conditions are met, the ECU grounds wire 213 and keeps it grounded until the throttle is advanced.
This option is available, but used in very few applications.
Option 5
Option 5 applies the retarder when the following conditions are met:
Wire 211 is connected to positive voltage.
The throttle position is near zero (fully closed).
The transmission output speed exceeds a programmed value.
When these conditions are met, the ECU grounds wire 213. This option is used primarily for
on-highway applications.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Retarder Enable and Output - Wires 211 and 213
Retarder Option Modifiers
Three modifiers (A, B, and AB) provide additional programming functions that add more flexibility to the four
retarder options. Modifiers are usually mentioned after the retarder option (Example: Option 1, Modifier AB).
Modifier A
With Modifier A, the retarder applies as programmed (depending on the retarder option). However, when a
turbine overspeed condition is sensed by the ECU, the following conditions exist:
During turbine overspeed, wire 213 becomes grounded, activating the retarder application relay. This
occurs regardless of other programmed conditions.
During turbine overspeed, wire 224 (a spare output wire in the cab harness) becomes grounded. This wire is
used to activate an overspeed warning circuit (light, buzzer, etc.) in the vehicle cab.
Modifier A does not always affect retarder operation, but lets the ECU ground wires 213 and 224 when a turbine
overspeed condition exists.
Modifier B
With Modifier B, the retarder applies as programmed, but the ECU commands the transmission to downshift
during retarder application.
The downshift procedure is known as Preselect Downshift.
The lowest downshifted range during Preselect Downshift can vary, depending on the PROM used.
Modifier AB
Modifier AB is a combination of Modifier A and Modifier B. When a turbine overspeed condition exists:
The ECU grounds wires 213 and 224, regardless of any other retarder operations. Wire 213 activates the
retarder apply circuit and wire 224 activates an overspeed warning circuit.
The ECU commands Preselect Downshift.
Modifier AB controls retarder, overspeed warning circuit, and Preselect Downshift operation regardless of
whether or not the retarder is applied.

COPYRIGHT 1994 GENERAL MOTORS CORP.

3-15

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Retarder Enable and Output - Wires 211 and 213
Additional Retarder Information
Cutoff Below Feature (Options)
Once applied, the retarder remains applied until the appropriate conditions no longer exist. The Cutoff Below
feature disables the retarder when output shaft speed falls below a programmed point.
When the vehicle slows to the Cutoff Below output speed point, the retarder is disabled.
The PROM must include the Cutoff Below feature for it to be active (ECIS tells whether or not the PROM
includes Cutoff Below).
Overspeed Signal (Modifiers A and AB)
In certain retarder option/modifier situations, the ECU is sensitive to overspeed conditions. Various PROMs are
available with different overspeed limits.
If the PROM contains overspeed signal programming, the overspeed RPM limit is also in the PROM.
Different PROMs are available for varying vehicle applications.
ECIS lists overspeed limits (in RPM) for specific PROMs.
Preselect to Range (Modifiers B and AB)
Preselect to Range is the range the transmission will downshift to during retarder operation.
The final downshift range can change depending on the PROM used.
ECIS lists the range downshifted to during Preselect to Range.

3-16

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Check Transmission Light - Wire 215
CAUTION: Connecting wire 215 directly to power causes damage to the ECU.

CHECK
TRANS LIGHT
+12 OR
+24 VOLTS

3H

WIRE 215
0.4 AMP MAX

ECU

FROM
OIL PRESSURE SWITCH
(+12 OR +24 VOLTS)

2120647.32
12/9/92

Wire 215 provides ground to the Check Transmission light relay during normal system operation.
The Check Transmission light relay is normally closed. The relay activation circuit is wired to receive
constant positive voltage when the engine is running. (This can be supplied from the oil pressure switch,
depending on ECU power wiring discussed earlier.)
Under normal operating conditions, wire 215 remains grounded, opening the relay power circuit (the Check
Transmission light is off).
When the system encounters problems or is placed in the diagnostic mode, wire 215 can become open,
closing the relays power circuit (the Check Transmission light is on).

COPYRIGHT 1994 GENERAL MOTORS CORP.

3-17

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Test Mode Switch - Wire 216A

DIAGNOSTIC
MODE SWITCH

2J
WIRE 216A

ECU

GROUND

2120647.24
12/8/92

When wire 216A is grounded, the Electronic Control attains the diagnostic mode.
An OEM-supplied switch grounds wire 216A when it is closed. During normal operation, the switch
is open.
The switch must offer less than 0.1 ohms resistance from contact to contact when closed.
The Check Transmission light flashes stored diagnostic codes when wire 216A is grounded.
Connecting and activating a Diagnostic Data Reader (DDR) to the Electronic Control also places the ECU
in the diagnostic mode. The Check Transmission light will flash any stored codes and the Digital Display
Unit (DDU), if used, will be de-activated.

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COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Range Commanded - Wire 217
CAUTION: Connecting wire 217 directly to power causes damage to the ECU.

TO
VEHICLE
SYSTEM
1E

WIRE 217
0.4 AMP MAX

ECU

+12 OR +24 VOLTS

RANGE
COMMANDED RELAY
WIRE 217 IS GROUNDED
WHEN IN THE SPECIFIED
RANGE(S)
2120647.33
12/9/92

Wire 217 is an output that goes from open to ground when the ECU commands a programmed range or ranges.
Wire 217 is normally programmed for Range Commanded. Range Commanded is an option that is used in
conjunction with a two-speed engine governor. When the Range Commanded circuit is energized, governed
high range engine speed is reduced.
Wire 217 can be used as a negative output signal whenever a programmed range is attained (it can be used
for operations other than Range Commanded).
ECIS lists which ranges ground wire 217.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Special Input - Wire 222

1K
SWITCH

WIRE 222
1A
WIRE 208

TO BATTERY
GROUND
TERMINAL

ECU
1B

WIRE 209

2120553.43
12/9/92

Wire 222 is an input wire that signals the ECU to activate one of three options (Quick-To-Neutral,
Neutral-To-Range Inhibit or Stall Check).
Wire 222 is a negative input - the ECU can attain one of three programmed options when wire 222 is either
grounded or open.
Options activated by wire 222 must be programmed - simply wiring the option doesnt activate it.
Wire 222 must be grounded (through a switch) directly to wires 208 and 209 (or to wire 309 in the Sealed
Plus II ECUs secondary harness).
ECIS lists the option (if any) that is programmed for the special input.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Special Input - Wire 222
Special Input Options
Quick-To-Neutral
When Quick-To-Neutral is programmed, opening wire 222 causes an immediate shift to neutral regardless of the
shift selector position or any other inputs.
The transmission operates normally as long as wire 222 is grounded. Quick-To-Neutral is attained when
wire 222 is open.
To de-activate Quick-To-Neutral, the shift selector must be placed in Neutral and wire 222 must then
be grounded.
This option can be programmed for use in primary mode, secondary mode or both primary and
secondary modes.
Quick-To-Neutral is commonly used in stationary equipment where a pump (or other device) must be
quickly disengaged.
Quick-To-Neutral is not allowed on mobile equipment.
Neutral-To-Range Inhibit
When Neutral-To-Range Inhibit is programmed, opening wire 222 while in neutral and at low output speed
will prevent the transmission from shifting into range. There are two options for de-activating
Neutral-To-Range Inhibit:
Option B1 requires wire 222 to be grounded and neutral to be selected before the transmission will go
into range.
Option B2 only requires wire 222 to be grounded - shift selector position does not matter.
Option B2 allows an immediate shift to range when wire 222 is grounded. Do not use this option unless
wire 222 is intentionally grounded by the vehicle operator (drivers seat switch, brake pedal switch, etc).
If the output speed exceeds a programmed value and the shift selector is moved into range,
Neutral-To-Range Inhibit is automatically de-activated, regardless of the programmed de-activation option
or wire 222 condition.
When Neutral-To-Range Inhibit is programmed, wire 222 must be grounded for the transmission to shift
into range.
Stall Check
When Stall Check is programmed, grounding wire 222 through an OEM-supplied switch shifts the transmission
into a high range with lock-up off. In this condition, the vehicle can be stall tested to troubleshoot power package
performance problems.
Always follow the appropriate procedures and safety guidelines when stall testing. Stall test for
troubleshooting purposes only.
To activate Stall Check, the vehicle must be stopped, neutral must be selected, wire 222 must be grounded
and the throttle must be closed. When these conditions are met, the shift selector must be moved to Drive.
To de-activate Stall Check, return the throttle to the closed position, shift to Neutral, then open wire 222.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Spare Output - Wire 224
CAUTION: Connecting wire 224 directly to power causes damage to the ECU.

TO
VEHICLE
SYSTEM
3K

ECU

WIRE 224
0.4 AMP MAX
+ 12 OR
+24 VOLTS

2120647.35
12/9/92

Wire 224 is an output that goes from open to ground when certain programmed conditions are met.
Wire 224 must be programmed as a spare output to be operational.
Wire 224 can be programmed for three options (Engine Overspeed, Oil Level/Pressure and Fire Truck
Special). Only one option can be chosen.
Wire 224 is directed from the ECU to a relay activation circuit. The relay can be either 12- or 24-volt, but
the current through the activation circuit must be limited to 0.4 amps by the coil resistance.
ECIS tells which option (if any) is programmed on wire 224.

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COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Spare Output - Wire 224
Spare Output Options
Engine Overspeed
Engine Overspeed is commonly programmed on wire 224. When an overspeed condition is detected, wire 224
goes from open to ground. When the overspeed condition is no longer present, wire 224 returns to open.
Overspeed condition RPM is programmable. ECIS lists the RPM where wire 224 goes to ground.
Using this option, wire 224 provides ground to a relay which activates an overspeed
warning/alert system.
Oil Level/Pressure
The Oil Level/Pressure option is not as common as the Engine Overspeed option. When the ECU recognizes a
valid low transmission oil level or pressure situation wire 224 goes from open to ground.
Using this option, wire 224 provides ground to a relay which activates a low oil level/pressure
warning device.
Fire Truck Special
This option is available with Sealed Plus II ECUs only.
If secondary mode is activated and Fire Truck logic is programmed as the secondary mode, wire 224 goes
to ground once the vehicle attains a forward range.
Wire 224 can activate a relay that turns on an Okay To Pump or similar warning/informational device
(Fire Truck Special is covered in more detail in the Optional Secondary Harness Interface section of
this document).

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Bi-Directional Communication Links (BDCLs) - Wires 238, 239, 240, and 241
1C

238

238

3B
ECU 1D

240

240

239

239

3C

241

241

ECU

TTCL
(Transmission to Transmission
Communication Link)

1C

238

532

3B

240

533

ECU 1D

239

534

3C

241

535

242

461
243

L
M
F
DDL

DDEC I
ENGINE
CONTROL

451
244

510

TECL
(Transmission to Engine
Communication Link)

2120647.36
12/9/92

Bi-Directional Communication Links (BDCLs) allow the Electronic Control to communicate with other engine or
transmission electronic controls.
BDCL is only operational when programmed for specific applications.
BDCL can provide either transmission-to-transmission communication (allowing one Electronic Control
system to control two transmissions) or transmission-to-engine communication (allowing the transmission
Electronic Control and the engines electronic control to share signals).
BDCL wires must be installed as twisted pairs (1 twist per 25 millimeters, or 1 twist per inch). Pairs must
be wires 238 and 240 and wires 239 and 241.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
Bi-Directional Communication Links (BDCLs) - Wires 238, 239, 240, and 241
BDCL Transmission-to-Transmission Communication
A BDCL programmed for transmission-to-transmission communication is primarily used in dual power package
vehicles or stationary equipment.
Transmission-to-transmission communication checks that shift schedules for both transmissions are not
more than one range apart.
BDCL Transmission-to-Engine Communication
A transmission-to-engine BDCL allows DDEC I and the Allison Transmission Electronic Control to
communicate. Three additional wires can be added to allow the transmission DDL connector to be used for
engine and transmission diagnosis.
The additional DDL wires (242, 243 and 244) do not need to be twisted like the other BDCL wires.
The transmission-to-engine communication link allows the DDEC I ECM to send throttle position data to
the transmission ECU.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
DDEC II Interface
DDEC II communicates with the ECU through a non-Allison supplied interface module. Two levels of interface
are available - Basic Interface and Maximum Feature Interface.
BASIC - THROTTLE SIGNAL ONLY
VEHICLE
INTERFACE
INTERFACE
MODULE

SHIFT
SELECTOR

1 3
1

ECU

THROTTLE POSITION SIGNAL

ECM

ENGINE

TRANSMISSION

*TRANSMISSION PROM MUST

BE COMPATIBLE WITH MUI
OR DDEC II ENGINE
CONTROLS (NOT DDEC I).

WIRE CONNECTION SUMMARY

ENGINE (ECM) 30-PIN CONNECTOR
WIRE NO.

1 THROTTLE POSITION

908

TRANSMISSION (ECU)*

CAVITY
J-3

WIRE NO.

PIN

CONNECTOR

TPS CONNECTOR

THE INTERFACE MODULE

(SHOWN IN PHANTOM)
IS OEM-SUPPLIED AND
INCLUDES CONNECTORS

WIRE 124
WIRE 104
A

DDEC II
HARNESS

WIRE 908

THROTTLE INTERFACE
MODULE

C
"THROTTLE POSITION" SECTION
OF ELECTRONIC CONTROLS I
CHASSIS WIRING HARNESS

PACKARD CONNECTOR TO BE OEM-SUPPLIED

1-CAVITY
SEALS (1)
TERMINALS (1)

12015791
12015323
12034051

PACKARD CONNECTOR ON MODULE

1-CAVITY CONNECTOR
SEALS (1)
TERMINALS (1)

12010996
12015323
12033674

WIRE 106A

PACKARD CONNECTOR INCLUDED

ON ELECTRONIC CONTROLS HARNESS
3-CAVITY
SEALS (3)
TERMINALS (3)

12015793
12015323
12033674

PACKARD CONNECTOR ON MODULE

3-CAVITY
SEALS (3)
TERMINALS (3)

12010717
12015323
12034051

2120647.37
12/9/92

Basic Interface
In the Basic Interface, DDEC II sends throttle position sensor information through an interface module to the
transmission ECU.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL CAB HARNESS INTERFACE
DDEC II Interface
THROTTLE SIGNAL - OUTPUT SPEED & ENGINE SPEED INHIBIT
INTERFACE
COMPONENT

VEHICLE INTERFACE
ENGINE SPEED INHIBIT

SHIFT
SELECTOR

TRANSMISSION OUTPUT SPEED

ECU

THROTTLE POSITION SIGNAL

ECM

ENGINE

TRANSMISSION

PACKARD CONNECTOR ON HARNESS

6-CAVITY CONNECTOR
SEALS (6)
TERMINALS (6)
CAVITY PLUG (1)
WIRE 438
GROUND
WIRE 606 OR
WIRE 972

WIRE 568
WIRE 903

PACKARD CONNECTOR ON MODULE

12015790
12015323
12034051
12010300

1-CAVITY CONNECTOR
SEALS (2)
TERMINALS (2)

12010972
12015323
12034051
WIRE 222

PACKARD CONNECTOR ON MODULE

A
B
C
D
E
F

12010975
12015323
12033674
12010300

6-CAVITY
SEALS (6)
TERMINALS (6)
CAVITY PLUG (1)

DDEC II
HARNESS

A
B

2-CAVITY CONNECTOR
SEALS (3)
TERMINALS (3)

ITEMS SHOWN IN PHANTOM

ARE CUSTOMER FURNISHED

A
B
C

WIRE 124
WIRE 104
WIRE 106A

PACKARD CONNECTOR ON MODULE

1-CAVITY CONNECTOR
SEAL (1)
TERMINAL (1)

12010996
12015323
12033874

PACKARD CONNECTOR ON HARNESS

PACKARD CONNECTOR ON HARNESS

12015791
12015323
12034061

PACKARD CONNECTOR ON MODULE

3-CAVITY CONNECTOR
SEALS (3)
TERMINALS (3)

12010973
12015323
12033674

THROTTLE POSITION
SECTION OF ATEC - 1
CHASSIS WIRING HARNESS

WIRE 908

1-CAVITY CONNECTOR
SEAL (1)
TERMINAL (1)

ATEC - 1 CAB
WIRING HARNESS

PACKARD CONNECTOR ON HARNESS

MAXIMUM FEATURE
THROTTLE INTERFACE
MODULE

CAVITY PLUG

WIRE 205

3-CAVITY CONNECTOR
SEALS (3)
TERMINALS (3)

12015793
12015323
12033674

12010717
12015323
12034051

2120647.38
12/9/92

Maximum Feature Interface

In the Maximum Feature Interface, DDEC II is sending the ECU throttle position sensor information through an
interface module (like Basic Interface), but provides additional communication signals.
Maximum Feature Interface sends transmission output shaft speed signals back to the DDEC II ECM.
These signals are used for cruise control/road speed limiting logic.
Maximum Feature Interface incorporates an integral engine speed switch which sends a signal to the ECU.
The signal provides input for the logic that prevents shifting into range above programmed
engine speeds.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Optional secondary harness interface connections are wired through the secondary wiring harness (300 series
wires), available only with Sealed Plus II ECUs. Options must be programmed and properly wired to operate.
Simply wiring the option will not enable it - the option must be programmed. If necessary, determine PROM
characteristics using ECIS.

Secondary Logic Return - Wire 309

CAUTION: Connecting wire 309 directly to power causes damage to the ECU.

WIRE 309

ECU

CONNECT TO
PROGRAMMED INPUT WIRES
USING OEM - SUPPLIED
SWITCHES

2120647.39
12/9/92

Secondary Logic Return (wire 309) is connected in parallel to a variety of switches. Wire 309 senses when any of
these switches are closed and carries a signal back to the ECU.
Only specified wires should be connected to wire 309.
Wire 309 and its related circuits should not be connected to chassis or frame ground.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Dual Mode Selection - Wires 313 and 315
SECONDARY MODE
SWITCHES

N
WIRE 313
R
WIRE 315

ECU
J

WIRE 309
BOTH SWITCHES MUST BE
CLOSED FOR SECONDARY
MODE OPERATION. BOTH
SWITCHES OPENED FOR
PRIMARY MODE.

2120647.40
12/9/92

The ECU changes to one of two pre-programmed secondary modes (Secondary Shift Schedule or Fire Truck
Special) when wires 313 and 315 are connected to wire 309 simultaneously.
The primary shift selector (and secondary shift selector, if used) must be in neutral to attain
secondary mode.
The ECU changes back to primary mode when wires 313 and 315 are opened with the selector(s)
in Neutral.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Dual Mode Selection - Wires 313 and 315
Secondary Mode Options
Secondary Shift Schedule
Secondary Shift Schedules can include:
Fuel economy schedules
Performance schedules
Fixed upshifts
Different number of available ranges
Second range start
Modulated upshifts
Fire Truck Special
Secondary mode is often programmed as the Fire Truck Special. Fire trucks utilize this option to operate water
pumps and related equipment. To attain a programmed Fire Truck Special, the transmission must be in
secondary mode.
Vehicles using Fire Truck Special can use a dash switch that connects wires 313 and 315 to wire 309
simultaneously. The vehicle can also use a combination of two switches - both on the dash, or one on the
dash, and one at the vehicle split-shaft PTO.
Example: The operator might have to connect wire 313 to wire 309 by activating a dash switch. The
operator then shifts the split-shaft PTO to engage the pump which (through a micro-switch) connects wire
315 to wire 309.
Once secondary mode is attained and the vehicle is placed in a forward range, wire 224 goes from open to
ground. This can be used to activate a light or similar device that lets the operator know the equipment is
ready to begin pumping.
The transmission responds by going into high range with the lockup clutch off.
The operator brings the engine to the desired RPM for pump operation. Once transmission output speed
reaches a programmed limit, the Electronic Control applies the lockup clutch. The pump is now being
driven by the transmission in high range, lockup on.
When dual shift selectors are used, a switch for wire 315 to wire 309 should be at one shift selector and
switch for wire 313 to wire 309 should be at another. This helps prevent unwanted mode changes.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Bed Hoist Interlock - Wire 305

E
WIRE 305

ECU

J
WIRE 309

HOIST LEVER SWITCH

SWITCH CLOSED FOR NORMAL
OPERATION
SWITCH OPEN TO ELIMINATE
REVERSE

2120647.41
12/9/92

When Bed Hoist Interlock is programmed, wires 305 and 309 must be connected (through an OEM-supplied
switch) for normal operation. When wires 305 and 309 are not connected, the transmission shifts from reverse
to neutral.
The OEM-supplied switch is mounted so that it is open when the vehicle dump bed is up and closed when
the dump bed is down.
Once Bed Hoist Interlock has been activated, the switch must be closed and neutral or any forward range
must be selected before reverse is selected and can be attained.
Bed Hoist Interlock does not inhibit shifts to a forward range just reverse. If Bed Hoist Interlock is
programmed and wires 305 and 309 are not connected (physically or through the OEM-supplied switch),
the transmission will not go into reverse. If the feature is programmed but not used, permanently connect
wires 305 and 309.
Bed Hoist Interlock is not available in software developed before 1987. Some earlier model harnesses do
not include wire 305.
Bed Hoist Interlock is standard in most off-highway hauling transmission applications
(beginning in 1987).
Bed Hoist Interlock is used to prevent inadvertent reverse operation while the vehicle is dumping.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Secondary Spare Input - Wire 303

C
WIRE 303
1A
WIRE 208

ECU

SWITCH

1B
WIRE 209

BATTERY
GROUND

2120647.42
12/9/92

A spare input is available in the secondary mode harness only if a secondary shift selector is not used. Connecting
wire 303 to wires 208 and 209 (direct ECU battery ground) enables the Secondary Spare Input, if programmed.
A Secondary Spare Input is not available on ECUs prior to model year 1987. Earlier model harnesses may
not include wire 303.
There is currently only one option available for Secondary Spare Input - Stall Check. If programmed,
Secondary Spare Input provides the same Stall Check feature as the Special Purpose Input (wire 222).

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Hold Feature - Wire 310

SWITCH
K
WIRE 310

ECU

WIRE 309

2120647.43
12/9/92

The Hold Feature can be attained (when programmed) by connecting wire 310 to wire 309 through an
OEM-supplied switch.
Two Hold Feature Options are available Loading Hold and Neutral Hold. Only one of these options can
be programmed, not both.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Hold Feature - Wire 310
Hold Feature Options
Loading Hold
During Loading Hold, normal downshifts occur, but upshifts occur on the Hold Upshift schedule.
When Loading Hold is programmed and attained, the transmission will not upshift beyond the range
currently attained. The transmission will downshift below the attained range as normal.
Opening wire 310 returns the system to the normal shift calibration.
Loading Hold is available in forward ranges only.
This application is often used while loading a scraper or other applications where an automatic upshift is
not desirable.
Neutral Hold
Neutral Hold inhibits shifting from neutral to any drive range when wires 310 and 309 are not connected and
output speed is low.
The transmission operates normally when wires 310 and 309 are connected through an
OEM-supplied switch.
The feature is de-activated when wires 310 and 309 are connected regardless of shift selector position. It
can also be de-activated if the output speed exceeds a programmed value and the shift selector is moved to
a drive range. This allows a shift to Drive even if wires 310 and 309 are not connected.
This Neutral Hold feature provides the same operational characteristics as Neutral-To-Range Inhibit Option
B2 (wired on Special Input Wire 222). Use wire 222 for this option unless the Special Input is used for
another option.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Forced Neutral - Wires 310 and 311
CAUTION: A neutral lamp (from wire 217) must be wired and warning signs must be posted in the vehicle
alerting operators of potential hazards.

SECONDARY MODE
SWITCHES
K
WIRE 310
L
WIRE 311

ECU
J

WIRE 309

2120647.44
12/9/92

When programmed, Forced Neutral is attained when wires 310 and 311 are simultaneously connected to wire
309. This allows the vehicle operator to command a shift from range to neutral without selecting Neutral on the
shift selector.
This option is only available in specific software (contact Allison Sales for availability information).
This option is only available for vehicles utilizing dual shift selectors.
WARNING: If the operator does not select Neutral and the OEM-supplied Forced Neutral circuitry fails, the
vehicle may suddenly attain range.
Opening the connection between wires 310, 311 and 309 returns the transmission to normal operation.
Forced Neutral is normally used in dual station garbage packers. The driver would be on the curb side of
the vehicle, stop the vehicle and apply a brake. The brake application connects wires 310 and 311 to 309,
and the transmission goes to Neutral. When the driver re-enters the vehicle and releases the brake, the
transmission re-attains range.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Manual Mode - Wires 311, 313 and 315
SWITCHES
L
WIRE 311
N
WIRE 313
R

ECU

WIRE 315
J
WIRE 309
ALL THREE SWITCHES MUST BE
CLOSED TO ATTAIN MANUAL MODE

2120647.45
12/9/92

Manual Mode is a programmed feature that blocks automatic shifts. Shifts are commanded based on the range
selected on the shift selector.
When wires 311, 313 and 315 are connected (through an OEM-supplied switch) to wire 309, the controls
attain Secondary Mode and (if programmed) Manual Mode.
Manual Mode is de-activated when wire 311 becomes open. If wires 313 and 315 remain connected to wire
309, the controls remain in Secondary Mode, but Manual Mode is not operational.
This feature is used primarily for stationary equipment with low inertia loads (oil field pumping
equipment, etc.). Manual Mode can also be used to diagnose clutch capacity, for stall checks, etc.
High inertia load equipment should not be operated in Manual Mode.
Access to the Manual Mode switch in these applications should be limited to service personnel.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Lockup On - Wire 314
SWITCHES
N
WIRE 313
R
WIRE 315
P

ECU

WIRE 314
J
WIRE 309
ALL THREE SWITCHES MUST BE
CLOSED TO ATTAIN LOCKUP ON

2120647.46
12/9/92

When wire 314 is connected to wire 309 while in Secondary Mode, lockup clutch operation is modified.
To attain Lockup On, wires 313, 315 and 314 must all be connected (through OEM-supplied switches)
to wire 309.
When Lockup On is activated and the transmission is in neutral, the lockup clutch remains applied at
all times.
When Lockup On is activated while the transmission is in range, lockup is applied for each
range attained.
Example: If the normal shift schedule is 1C, 2C, 3C, 3L, 4C, 4L, 5L, the Lockup On shifting mode
becomes 1C, 1L, 2C, 2L, 3C, 3L, 4C, 4L, 5L.
Opening wire 314 de-activates Lockup On, but if wires 313 and 315 remain connected to wire 309, the
controls stay in Secondary Mode.
This option is often used when operating a converter-driven PTO in neutral.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Lockup Off - Wire 312
SWITCHES
N
WIRE 313
R
WIRE 315
M

ECU

WIRE 312
J
WIRE 309
ALL THREE SWITCHES MUST BE
CLOSED TO ATTAIN LOCKUP OFF

2120647.47
12/9/92

When wire 312 is connected to wire 309 while in secondary mode, the lockup clutch will remain off.
Opening wire 312 returns the transmission to normal lockup operation, but Secondary Mode remains
attained as long as wires 313 and 315 are connected to wire 309.
If Lockup On and Lockup Off are both activated, Lockup On is dominant.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Secondary Shift Selector Lamp Circuit - Wires 317, 318 and 319

12-VOLT SYSTEMS
GROUND

DASH CONTROL

GROUND

317 10

24-VOLT SYSTEMS
DASH CONTROL

318 13

NOT USED

319 14

GROUND

317 10

318

319 14

PUSH BUTTON
SHIFT SELECTOR

PUSH BUTTON
SHIFT SELECTOR

12-VOLT SYSTEMS
GROUND

DASH CONTROL

GROUND

317 1F

13

24-VOLT SYSTEMS
DASH CONTROL

318 2F
319 3F
LEVER SHIFT SELECTOR

NOT USED

GROUND

317 1F
318 2F
319 3F
LEVER SHIFT SELECTOR

2120647.48
12/8/92

If a secondary shift selector is used, illumination lamp power must be provided through the secondary mode
harness interface.
In 12-volt systems, wires 317 and 319 are grounds - wire 318 supplies voltage to the circuit through the
vehicle dash illumination rheostat.
In 24-volt systems, wire 319 is ground and wire 318 is not used -wire 317 supplies 24 volts to the circuit
through the vehicle dash illumination rheostat.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Secondary Shift Selector Power - Wires 321, 323 and 324
15

SECONDARY
PUSH
BUTTON
SHIFT
SELECTOR

12

WIRE 324
(+ 24V IGNITION)

USE ONLY ONE

WIRE 321
(+ 12V IGNITION)

WIRE 202A

8
WIRE 323

WIRE 223A

TO
ECU

2120647.49
12/9/92

Secondary shift selector power is supplied to the shift selector from the vehicle master switch and directly from
the battery positive terminal.
Wire 323 should be connected directly to the battery positive terminal (or to ECU power, wires 202A
and 223A).
Wire 324 should be used on 24-volt systems. Power to this wire should be supplied through the vehicle
master switch.
Wire 321 should be used on 12-volt systems. Power to this wire should be supplied through the vehicle
master switch.

2A
1C

SECONDARY
LEVER
SHIFT
SELECTOR

WIRE 324
(+ 24V IGNITION)

USE ONLY ONE

WIRE 321
(+ 12V IGNITION)

WIRE 202A

1D
WIRE 323

WIRE 223A

TO
ECU

2120647.50
12/9/92

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

VEHICLE INTERFACE
OPTIONAL SECONDARY HARNESS INTERFACE
Secondary Shift Selector Neutral Start Provision - Wire 322
CAUTION: Connecting wires 231 and/or 322 directly to power causes damage to the ECU.

PUSH
BUTTON
SHIFT
SELECTOR

WIRE 231
0.5 AMP MAX

NEUTRAL START
CIRCUIT IN VEHICLE

PUSH
BUTTON
SHIFT
SELECTOR

+ 12 OR
+ 24 VOLTS
WIRE 322
0.5 AMP MAX

1A

LEVER
SHIFT
SELECTOR

WIRE 231
0.5 AMP MAX

NEUTRAL START
CIRCUIT IN VEHICLE

1A

LEVER
SHIFT
SELECTOR

+ 12 OR
+ 24 VOLTS
WIRE 322
0.5 AMP MAX

2120647.51
12/9/92

When a secondary shift selector is used, the neutral start circuit should include a second relay activated by the
secondary shift selector.
When the selector is placed in Neutral, wire 322 goes from open to ground. This energizes the relays
activation circuit, closing the relay for the neutral start circuit.
The relay power circuit must be connected in series to the primary neutral start circuit. This prevents the
vehicle from starting if either shift selector is not in Neutral.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

SELF-DIAGNOSTICS
TROUBLE CODES
Trouble codes are generated and stored in the ECU memory when the Electronic Control self-diagnostics sense
system problems. They can also be generated during system installation and initial operation. Trouble codes fall
into one of two categories - soft or hard.
Soft codes do not cause inhibited transmission operation, but they might make the Check Transmission light
come on, if the vehicle is equipped with one. Soft codes are stored in memory and indicate potential
system problems.
Hard codes cause the Do Not Shift light (and the Check Transmission light, if equipped) to come on. Hard codes
indicate a problem that can be potentially damaging or dangerous. When hard codes exist, theyre logged in
memory and transmission operation is inhibited to limit potential damage.
To retrieve codes using the ProLink diagnostic tester:
1. Connect the ProLink to the Electronic Control DDL.
2. Select the transmission type from the Main Menu.
3. Press Function to enter the Function Selections Menu.
4. Scroll until Diagnostic Codes appears, then press Enter.
The display will list any diagnostic codes stored in memory.
To clear codes using the ProLink diagnostic tester:
1. Turn the vehicle off.
2. Connect the ProLink to the DDL connector.
3. Start the vehicle.
4. Make sure the vehicle parking brake and service brake are applied, then move the shift selector from
neutral to reverse, then back to neutral.
To retrieve codes without the ProLink (the installation must include a Check Transmission light):
1. Start the vehicle and run the engine at idle with the shift selector in neutral.
2. Place and hold the Electronic Control test switch in the on position.
3. The Check Transmission light will flash the most important diagnostic code if one is present
(Example: flash-pause-flash-flash-flash indicates Code 13).
NOTE:

The Check Transmission light not will flash if no codes are present. There is no Code 25 for No
Codes as in DDEC.

To clear codes without the ProLink:

1. Turn the vehicle off.
2. Place the Electronic Control diagnostic test switch in the on position.
3. Restart the vehicle.
4. Make sure the park brake and service brake are applied, then shift from neutral to reverse, then
back to neutral.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

TROUBLESHOOTING - TROUBLE CODES PRESENT
INTRODUCTION
The Electronic Controls self-diagnostic feature provides troubleshooting information in the form of trouble
codes. Trouble codes identify general problem areas and provide a starting point for system troubleshooting.
NOTE:

This manuals Self-Diagnostics section provides detailed trouble code information, including
code accessing and clearing procedures. Review this section before proceeding.

WHAT TO CHECK FIRST

Before spending a lot of time troubleshooting, check these simple items that can cause a wide variety of
trouble codes:
Make sure the shifter is in the appropriate range.
Check the transmission oil level.
Make sure the vehicles batteries are properly connected and charged.
Make sure wiring harness connections are correct and secure.
Check related OEM equipment for proper installation and operation.
Check for proper electronic option operation and vehicle interface wiring.
Once the above items are repaired or found to be okay:
Clear codes from the system.
Road test the vehicle.
Check for code re-occurrence.
If the code still exists, begin troubleshooting procedures. If the code no longer exists, the problem may be
intermittent (refer to this manuals Troubleshooting - Intermittent Trouble Codes section).

TROUBLESHOOTING STEPS
Specific troubleshooting steps for each trouble code are contained in Appendix A of this manual. This
information includes:
A description of what the code means, and possible system reactions to the code.
Potential non-electronic causes of the code (if applicable).
Potential electronic causes of the code.
Detailed, isolated wiring schematics of circuits, components and connectors related to the suspect area.
Troubleshooting steps, starting with the easiest, most common sense items to check.
For each existing trouble code, refer to the appropriate chart in Appendix A. Use the code description to
understand what the code means. Next, check for potential non-electronic causes, if applicable. Use the summary
of potential electronic causes as an overview of the troubleshooting steps. Finally, use the schematics, charts and
Troubleshooting Steps to isolate problems.
Troubleshooting steps generally consist of component, circuit and wire checks using a digital volt-ohmmeter. An
understanding of basic electricity and electrical checks is critical to successful troubleshooting.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

TROUBLESHOOTING - TROUBLE CODES PRESENT
Code

5-2

Description

12

Low Lube Pressure

13

Low Battery Voltage

14

Forward Pressure Switch

15

Reverse Pressure Switch

21

Throttle Sensor

22

Speed Sensor

23

Primary Shift Selector

24

Oil Temperature

31

Secondary Shift Selector

32

Direction Signals

33

Temperature Sensor

34

PROM Check

41

J Solenoid/Circuitry

42

F Solenoid/Circuitry

43

D Solenoid/Circuitry

44

C Solenoid/Circuitry

45

B Solenoid/Circuitry

46

A Solenoid/Circuitry

51

G (Lockup) Solenoid/Circuitry

52

E (Trim Boost) Solenoid/Circuitry

53

H (Neutral) Solenoid/Circuitry

54

Latching Solenoid Chain

61/63

G Solenoid/Circuitry

62

F Solenoid/Circuitry

66

Transmission Engine Communication Link (TECL)

69

Software Error

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

TROUBLESHOOTING - TROUBLE CODES PRESENT
Wire And Circuit Check Procedures
Wire and circuit checks help locate the source of electrical problems.
Resistance checks are used to determine circuit and component resistances.
Continuity checks determine whether a circuit is open, closed, or shorted to another wire or ground.
These checks require the use of a high impedance digital volt-ohmmeter and, sometimes, a jumper wire set.
CAUTION: Refer to the volt-ohmmeter manufacturers operating instructions to avoid possible meter and
system damage.

CAUTION: Never insert volt-ohmmeter test leads directly into electronic control connector terminals. This
spreads the terminal and creates bad connections. Always use the appropriate jumper lead from
the approved jumper wire set (special tool number J34521).

Resistance Checks
WIRING HARNESS
CONNECTOR
SOLENOIDS

10

VOLT-OHM
METER

9-20 OHMS ON-HIGHWAY

12-24 OHMS OFF-HIGHWAY
Circuit has continuity.

INFINITE (

) OHMS

Circuit does not have continuity due to a

broken wire (open circuit). VOM reading is
very high (infinite ohms). This could also be
due to an open solenoid coil or bad connection.
2120721.01
11/1/94

To check resistance, the circuit or component must be de-energized. An ohmmeter lead should be placed on each
side of the tested circuit. Isolate the circuit or component. If several components are connected together, the
resistance reading may not be accurate.
Resistance is an important factor for electronic control operation, and it can also be a critical troubleshooting
measurement. One way the ECU monitors circuit status is by reading the circuits resistance. When trouble codes
exist, circuit or component resistances can be checked and compared to design specifications.
COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

TROUBLESHOOTING - TROUBLE CODES PRESENT
Continuity Checks
CONNECTOR
WIRING HARNESS
JUMPER

CONNECTOR

VOLT-OHM
METER

0 OHMS
Circuit has continuity. Jumper from
102 or 120 to another wire produces a complete
circuit. VOM reading is near zero ohms.

OHMS
Circuit does not have continuity due to a
broken wire (open circuit). VOM reading is
very high (infinite ohms).
2120721.02
5/19/93

Continuity checks are performed on de-energized circuits, just like resistance checks. An ohmmeter lead should
be placed on each side of the tested circuit.
Continuity checks are similar to resistance checks, but specific resistance readings are not as critical. Continuity
indicates the presence of a complete (closed) circuit, but the resistance of the circuit (to a point) is not important.
Continuity is indicated by minimal resistance readings. Circuits with infinite resistance are open - no
continuity exists.
Jumper wires can simplify harness check procedures. Since most harnesses are long, its difficult to place
ohmmeter leads on each harness end and check for continuity. Jumper wires can be used to create circuits and
isolate potential problems.

5-4

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

TROUBLESHOOTING - TROUBLE CODES PRESENT
Checking For Shorts
CONNECTOR
WIRING HARNESS
CONNECTOR

SHORTED TO
GROUND ON
METAL FRAME RAIL

WIRES
SHORTED
TOGETHER

GROUND
TO METAL
FRAME RAIL

VOLT-OHM
METER
+

0 OHMS

0 OHMS

Two wires have frayed and are shorted together.

Continuity beeper of VOM will sound, or reading will go to
zero ohms when these two wires are probed with the VOM.

Harness has been chafed and one or more wires are

shorted to ground. VOM continuity beeper will go to
zero ohms when meter is probing between
this wire and chassis ground.
2120721.03
5/19/93

Continuity checks are also used to identify shorts in a circuit. When a circuits wire is not insulated against an
alternate path of current flow, the circuit is said to be shorted.
For example, if a circuit has two wires running right against each other (like a wiring harness) and both wires
insulation broke at the same spot, the conductors would short together. This causes current to flow from one wire
directly to the other wire, bypassing the rest of the circuit. Shorts between wires, or from a wire to ground, can
cause continuity to exist where it should not.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

TROUBLESHOOTING - INTERMITTENT TROUBLE CODES
Intermittent codes are the result of conditions which are not always present. When conditions causing the code
exist, the code is logged in memory. The code stays until its manually cleared.
Use the code number to identify the general area of concern. For instance, if Code 21 intermittently appears,
focus on the throttle position sensor circuit and check for:
Dirty, damaged harness connectors and terminals.
Terminals not fully seated in connectors.
Damaged harnesses (due to poor routing, chafing, excessive heat, tight bends, etc.).
Improperly mounted components.
Poor connector seals (where applicable).
Exposed harness wires.
Accessories or components creating Electro-Magnetic Interference (EMI).
To locate the cause of intermittent codes, it sometimes helps to use the volt-ohmmeter on the suspect component
or circuit and simulate operating conditions. Wiggle, pull, bump, and bend the component or wire while watching
the meter.
Use the applicable Troubleshooting Steps in Appendix A as a guide for checking potential problem areas.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

TROUBLESHOOTING - NO TROUBLE CODES PRESENT
If the transmission is not performing properly and no codes are generated, start with the same basic items checked
when trouble codes are present, including:
Oil level.
Range selection.
Batteries.
Electrical connections.
Component installation.
Check these additional items to determine if the problem is caused by a vehicle system other than the
Electronic Control:
Is the ECU receiving proper voltage and ground?
Is the engine properly tuned?
Is fuel flow to the engine adequate?
Is air flow to the radiator and transmission cooler unrestricted?
Is the parking brake properly connected?
Are there signs of leaking oil under the vehicle, and where does it originate?
Are there any other obvious concerns about the vehicle or transmission?
NOTE:

Always consider programmed options that might affect vehicle operation. For instance, if a
vehicle programmed with Bed Hoist Interlock will not go into Reverse, the interlock switch
might be open, preventing Reverse without setting a code.

After these checks are made, refer to this manuals Appendix B, Troubleshooting Steps - No Trouble Codes.
These charts address specific vehicle complaints, probable causes and remedies. It may be necessary to refer to
the transmissions specific Service Manual or Parts Catalog for more information.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
The following pages include detailed troubleshooting information for each trouble code. Codes are listed in
numerical order. A thorough understanding of Electronic Control components and operation is necessary for
successful troubleshooting.
NOTE:

Refer to sections 1 through 5 in this manual for important, detailed operational and preliminary
troubleshooting information.

TROUBLESHOOTING PRECAUTIONS
CAUTION: Make sure the engine and ignition are always off before any harness connectors are disconnected
or connected. Removing or installing connectors when the system is on can cause damage and
set inadvertent codes.
CAUTION: When disconnecting connectors, dont pull on wires.
CAUTION: When welding on electronically-controlled vehicles:
Remove the ECU connectors from the ECU.
Dont connect welding cables to electronic components.
Dont weld on electronic components.
Protect electronic components from heat, sparks, impact, etc.
Remove components, if necessary.
CAUTION: Do not jump start the vehicle using arc welding equipment.
CAUTION: Be careful not to damage terminals by probing directly with ohmmeter test leads. Always use the
appropriate jumper lead from the approved jumper wire set (special tool J34521).
NOTE:

Watch carefully for damaged or dirty connector terminals. This can cause poor or
intermittent connections.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-1

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 12 - LOW LUBE PRESSURE/LOW OIL LEVEL (ON-HIGHWAY ONLY)

J1A
LOCATION-VALVE BODY

ECU
H
E

I
N
T
E
R
N
A
L

CHASSIS WIRING
HARNESS CONNECTOR
LUBE
LEVEL

B
U
L
K
H
E
A
D

C
O
N
N
E
C
T
O
R

122
101

VIOLET
RED

NOTE:

3N
2N +

J1B

The transmission is equipped

with only 1 of the 3 switch types.

W
I
R
I
N
G

FLUIDIC

ECU
J1B CHASSIS
HARNESS

J1B CONNECTOR

A-2

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 12 - LOW LUBE PRESSURE/LOW OIL LEVEL (ON-HIGHWAY ONLY)
This code indicates that the ECU senses a low lube pressure or low oil level signal. The type of signal depends on
which oil pressure or level switch the transmission uses.
Some potential non-electronic causes include:
Low transmission oil level.
Low oil pressure (caused by clogged filters, a worn charging pump, faulty main pressure regulator, etc.).
If necessary, verify that the transmissions hydraulic system is functioning properly by performing pressure tests.
Refer to the appropriate Allison Transmission Service Manual for pressure testing procedures.
Some potential electronic control causes include:
Opens or shorts in chassis harness wires 122 and 101.
Opens or shorts in the electro-hydraulic valve body circuit between terminals H and E.
Faulty transmission oil pressure or level switch.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Determine which type of oil pressure or level switch the transmission uses. Refer to ECIS and the appropriate
Parts Manual to determine which switch the transmission uses.
a. The transmission will be equipped with only one type of switch - Lube Pressure, Low Oil Level/Pressure
Sensor or Fluidic Oil Level Sensor.
2. Remove the chassis wiring harness connector (J1B) from the ECU.
3. Use an ohmmeter to check for continuity between terminals 3N and 2N in the J1B connector.
Record your results.
4. Make sure the vehicles parking brake is applied, chock the vehicles wheels, and start the engine. With the
transmission at normal operating temperature, check for continuity between terminals 3N and 2N in the J1B
connector. Record your results.
NOTE:

Starting the engine with the J1B connector disconnected may create codes. Clear all codes prior
to road testing the vehicle.

5. Refer to the Switch Continuity Chart to determine whether your continuity readings are correct.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-3

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 12 - LOW LUBE PRESSURE/LOW OIL LEVEL (ON-HIGHWAY ONLY)

Switch Type

Continuity
Engine Running

Continuity
Engine Stopped

Code Info

Lube Pressure
Switch

Yes (Switch Closed)

No (Switch Open)

Open circuit
generates code

No (Switch Open)

No (Switch Closed)

Closed circuit
generates code

Yes (Switch Closed)

Yes (Switch Closed)

Open circuit
generates code

Low Oil Level/

Pressure Sensor

Fluidic Oil
Level Sensor

A-4

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 12 - LOW LUBE PRESSURE/LOW OIL LEVEL (ON-HIGHWAY ONLY)
6. If continuity readings are incorrect, check the chassis wiring harness.
a. Check chassis wires 122 and 101 for opens, shorts to each other, shorts to other wires and shorts
to ground.
b. Check terminals 3N and 2N for damage, dirt or corrosion.
c. Check terminals H and E at the bulkhead connector for damage, dirt or corrosion.
Isolate and repair problems as needed.
7. If continuity readings are incorrect and the chassis harness is okay, check the bulkhead connector and internal
wiring harness.
a. Disconnect the switch to isolate the internal wiring harness.
b. Check the internal wiring harness (between terminals H and E) for opens, shorts to each other, shorts to
other wires and shorts to ground.
Isolate and repair problems as needed.
8. If continuity readings are incorrect and the chassis harness, bulkhead connector and internal wiring harness
are okay, check the switch.
a. Remove or isolate the switch.
b. Use an ohmmeter to check the switchs continuity with no pressure present.
1) Lube Pressure Switches should show no continuity.
2) Low Oil Level/Pressure Sensors should show no continuity.
3) Fluidic Oil Level Sensors should show continuity.
c. Apply 6 to 12 psi of air pressure to the switch and check continuity.
1) Lube Pressure Switches should show continuity.
2) Low Oil Level/Pressure Sensors should show continuity.
a) Check the bi-metal strip carefully for damage and proper operation.
3) Fluidic Oil Level Sensors should show no continuity.
If continuity readings are incorrect, replace the switch.
9. If continuity readings are correct, and possible mechanical causes have been checked, replace the ECU. If
replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it, road testing the vehicle,
and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-5

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 13 - LOW BATTERY VOLTAGE
Option 1
CHECK
TRANS

3H
215
202A
223A
208
209

2A
2B
1A
1B

ECU

OIL PRESS*

+IGN

BATTERY
VOLTAGE
12 OR 24
VOLTS

8A

*Oil pressure switch is only

required for emergency and
off-highway vehicle applications.

12 VOLTS FROM
BATTERY OR
VOLTAGE
CONVERTER

DIRECT TO
BATTERY
GROUND

2120647.19
5/28/93

Option 2
CHECK
TRANS

215

OIL
PRESSURE
SWITCH*

DIODE

202A
223A
208
209

IGNITION/MASTER
SWITCH

3H

2A
2B
1A
1B

ECU

8 AMP
*Oil pressure switch is only
required for emergency and
off-highway vehicle applications.

12 VOLTS FROM
BATTERY OR
VOLTAGE CONVERTER
BATTERY
VOLTAGE
12 OR 24 VOLTS

DIRECT TO
BATTERY GROUND
2120647.20
5/28/93

These are the two recommended interface options. Your vehicle wiring may vary.

A-6

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 13 - LOW BATTERY VOLTAGE
This code indicates that the ECU senses insufficient voltage.
Some potential non-electronic control causes include:
Bad batteries.
Faulty vehicle charging system.
Bad battery cable connections.
Faulty power supply.
Vehicle components or accessories causing excessive electrical system drain.
Check these items and make repairs as needed before troubleshooting the electronic control.
Some potential electronic control causes include:
Opens or shorts in cab harness wires 202A, 223A, 208 and 209.
Faulty vehicle interface circuitry for wires 202A, 223A, 208 and 209.
Non-dedicated ECU power or ground wiring (ECU power or ground shared by another component rather
than directly wired to the power source).
Faulty ECU.
NOTE:

Wires designated with a letter suffix (202A, for example) are spliced. When checking for shorts
to other wires, refer to this manuals detailed wiring schematics to determine which terminals
should show continuity.

TROUBLESHOOTING STEPS
1. Remove the cab wiring harness connector (J1A) from the ECU.
2. Check for sufficient positive voltage at J1A terminals 2A and 2B.
a. Connect one voltmeter lead to the negative side of the battery or a known good ground, and the other lead
to terminal 2A. If voltage is low (see Electronic Control Voltage Requirements Chart), check wire 202A
and its related circuitry for opens and shorts. If a power supply or converter is used, check it carefully for
proper operation.
b. Connect one voltmeter lead to the negative side of the battery or a known good ground, and the other lead
to terminal 2B. If voltage is low, check wire 223A and its related circuitry for opens and shorts. If a
power supply or converter is used, check it carefully for proper operation.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-7

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 13 - LOW BATTERY VOLTAGE

Electronic Control Voltage Requirements

Minimum
Maximum Continuous
Maximum Intermittent

10 Volts
16 Volts
19 Volts

J1B CONNECTOR

J1A CAB
HARNESS

ECU

A-8

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 13 - LOW BATTERY VOLTAGE
3. Check for sufficient ground at J1A terminals 1A and 1B.
a. Connect one voltmeter lead to the positive side of the battery or a known good positive voltage source,
and the other lead to terminal 1A. If voltage is low, check wire 208 for opens and shorts. If a power
supply or converter is used, check it carefully for proper operation.
b. Connect one voltmeter lead to the positive side of the battery or a known good positive voltage source,
and the other lead to terminal 1B. If voltage is low, check wire 209 for opens and shorts. If a power
supply or converter is used, check it carefully for proper operation.
Isolate and repair problems as needed.
4. If battery voltage to the ECU is okay, and the vehicles batteries, charging system, and electrical accessories
are okay, replace the ECU. If replacing the ECU fixes the problem, verify the old ECU is bad by
reinstalling it, road testing the vehicle, and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-9

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 14 - FORWARD PRESSURE SWITCH (ON-HIGHWAY ONLY)

J1A
LOCATION-VALVE BODY

CHASSIS WIRING
HARNESS CONNECTOR

ECU
F
E

I
N
T
E
R
N
A
L

B
U
L
K
H
E
A
D

118
101

BLUE
RED

3P
2N +

J1B

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
FWD PRESSURE SWITCH

ECU
J1B CHASSIS
HARNESS

J1B CONNECTOR

A-10

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 14 - FORWARD PRESSURE SWITCH (ON-HIGHWAY ONLY)
This code means that the ECU is receiving signals from the forward and reverse pressure switches when the
transmission is in reverse, or the ECU is not receiving a signal from the forward pressure switch when the
transmission is in forward and throttle position is greater than a preset percentage.
Some potential non-electronic causes include:
Internal hydraulic problems sending or inhibiting pressure to the forward or reverse pressure switches at the
wrong time (usually accompanied by faulty transmission performance).
If necessary, verify that the transmissions hydraulic system is functioning properly by performing pressure tests.
Refer to the appropriate Allison Transmission Service Manual for pressure testing procedures.
Some potential electronic control causes include:
Opens or shorts in chassis harness wires 118 and 101.
Opens or shorts in the electro-hydraulic valve body circuit between terminals F and E.
Faulty forward pressure switch.
Faulty ECU.
NOTE:

Its common for a Code 32 to be stored when Code 14 is present.

TROUBLESHOOTING STEPS
1. Verify the presence of Code 14 by clearing the ECU diagnostic memory, then road testing the vehicle.
Operate the vehicle at a minimum of 60% full throttle during the road test.
a. Re-check for codes. If Code 14 is present, continue with the troubleshooting steps.
b. If Code 14 is not present, the problem may be intermittent.
2. Remove the chassis harness connector (J1B) from the ECU, and remove the bulkhead connector from
the transmission.
3. Check chassis harness wires 118 and 101 for opens, shorts to each other, shorts to other wires and shorts
to ground.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-11

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 14 - FORWARD PRESSURE SWITCH (ON-HIGHWAY ONLY)

A-12

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 14 - FORWARD PRESSURE SWITCH (ON-HIGHWAY ONLY)
4. If the chassis harness is okay, check the internal wiring harness.
a. Leave the chassis harness unplugged from the bulkhead connector and disconnect the internal wiring
harness from the forward pressure switch.
b. Check the internal wiring harness wires between the switch and terminals F and E for opens, shorts to
each other, shorts to other wires and shorts to ground.
Isolate and repair problems as needed.
5. If the internal wiring harness is okay, check the forward pressure switch.
a. Remove the forward pressure switch.
b. Check switch continuity with no pressure present (the switch is normally open - no continuity
should exist).
c. Check continuity while applying 25 to 35 psi of air pressure to the switch (the switch should close and
show 0 ohms resistance - continuity should exist).
1) Make sure the switch is not closing at low pressure. The switch should remain open until 25 psi of air
is applied.
Replace the switch, if necessary.
6. If no problems are found, replace the ECU. If replacing the ECU fixes the problem, verify the old ECU is
bad by reinstalling it, road testing the vehicle, and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-13

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 15 - REVERSE DIRECTION SWITCH (ON-HIGHWAY ONLY)

J1A
LOCATION-VALVE BODY

CHASSIS WIRING
HARNESS CONNECTOR

ECU
G
E

I
N
T
E
R
N
A
L

B
U
L
K
H
E
A
D

116
101

YELLOW
RED

1R
2N +

J1B

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
REVERSE PRESSURE SWITCH

ECU
J1B CHASSIS
HARNESS

J1B CONNECTOR

A-14

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 15 - REVERSE DIRECTION SWITCH (ON-HIGHWAY ONLY)
This code means that the ECU is receiving signals from the forward and reverse pressure switches when the
transmission is in forward, or the ECU is not receiving a signal from the reverse pressure switch when the
transmission is in reverse and throttle position is greater than a preset percentage.
Some potential non-electronic causes include:
Internal hydraulic problems sending or inhibiting pressure to the forward or reverse pressure switches at the
wrong time (usually accompanied by faulty transmission performance).
If necessary, verify that the transmissions hydraulic system is functioning properly by performing pressure tests.
Refer to the appropriate Allison Transmission Service Manual for pressure testing procedures.
Some potential electronic control causes include:
Opens or shorts in chassis harness wires 116 and 101.
Opens or shorts in the electro-hydraulic valve body circuit between terminals G and E.
Faulty reverse pressure switch.
Faulty ECU.
NOTE:

Its common for a Code 32 to be stored when Code 15 is present.

TROUBLESHOOTING STEPS
1. Verify the presence of Code 15 by clearing the ECU diagnostic memory, then road testing the vehicle.
Operate the vehicle at a minimum of 60% full throttle in reverse during the road test.
a. Re-check for codes. If Code 15 is present, continue with the troubleshooting steps.
b. If Code 15 is not present, the problem may be intermittent.
2. Remove the chassis harness connector (J1B) from the ECU, and remove the bulkhead connector
from the transmission.
3. Check chassis harness wires 116 and 101 for opens, shorts to each other, shorts to other wires and shorts to
ground. Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-15

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 15 - REVERSE DIRECTION SWITCH (ON-HIGHWAY ONLY)

A-16

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 15 - REVERSE DIRECTION SWITCH (ON-HIGHWAY ONLY)
4. If the chassis harness is okay, check the internal wiring harness.
a. Leave the chassis harness unplugged from the bulkhead connector and disconnect the internal wiring
harness from the reverse pressure switch.
b. Check the internal wiring harness wires between the switch and terminals G and E for opens, shorts to
each other, shorts to other wires and shorts to ground.
Isolate and repair problems as needed.
5. If the internal wiring harness is okay, check the reverse pressure switch.
a. Remove the reverse pressure switch.
b. Check switch continuity with no pressure present (the switch is normally open - no continuity should
exist).
c. Check continuity while applying 25 to 35 psi of air pressure to the switch (the switch should close and
show 0 ohms resistance - continuity should exist).
1) Make sure the switch is not closing at low pressure. The switch should remain open until 25 psi of air
is applied.
Replace the switch, if necessary.
6. If no problems are found, replace the ECU. If replacing the ECU fixes the problem, verify the old ECU is
bad by reinstalling it, road testing the vehicle, and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-17

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 21 - THROTTLE POSITION SENSOR

TPS
J1A

9K TO 15 K

A
B
C

+5V
GND

RED
YELLOW
BLACK

124
104
106A

1P
2P
1N

ECU
J1B

9000/15000 - TERMINALS A TO C

A-18

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 21 - THROTTLE POSITION SENSOR
This code indicates that the ECU is receiving an incorrect signal from the throttle position sensor or its related
circuits. This code is set if throttle counts are in either of the error zones.
When an extreme stroke condition is detected, a trouble code is logged in the ECUs memory. The throttle
percentage is set to 100% or 0%, depending on the situation, so you may get either closed throttle shift points or
full throttle shift points.

Before troubleshooting:
Cycle the vehicles master/ignition switch on and off several times to allow the throttle sensor to selfadjust. Clear the code and check for re-occurrence.
Check throttle sensor linkage for proper installation, operation, wear, binding, etc.
Inspect the throttle sensor cable for proper installation, binding or damage.
Check the throttle sensor cable for proper adjustment.
NOTE:

If the vehicle is equipped with DDEC II, check the OEM-supplied interface module for proper
installation and calibration.

Some potential electronic control causes include:

Faulty throttle position sensor.
Opens or shorts in chassis harness wires 124, 104 and 106A.
Faulty ECU.
NOTE:

Wires designated with a letter suffix (106A, for example) are spliced. When checking for shorts
to other wires, refer to this manuals detailed wiring schematics to determine which terminals
should show continuity.

TROUBLESHOOTING STEPS
1. Check the throttle position sensor.
a. With the chassis harness disconnected, check resistance between throttle position sensor terminals A and
C. Resistance should be 9000 to 15,000 ohms.
b. Connect the ohmmeter leads to throttle sensor terminals A and B. Stroke the sensor very slowly from
closed throttle, to full throttle, back to closed throttle.
1) Watch for a smooth transition while stroking the throttle. Small, quick changes may not be seen with
a digital meter. An analog (needle type) meter can be used for a more accurate check.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-19

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 21 - THROTTLE POSITION SENSOR

TPS Counts
255 COUNTS

0 COUNTS

233 COUNTS

14 COUNTS

APPROX.
0.75 INCH
STROKE

ERROR
ZONE

IDLE
0

0.2 INCH

ERROR
ZONE

FULL
THROTTLE
1.8 INCHES

1.9 INCHES

APPROX.
0.5 INCH
FULLY
RETRACTED

FULLY
EXTENDED

2120647.10
12/8/92

TPS Adjustment
ENGINE
FUEL CONTROL
LEVER

MINIMUM 0.25 IN.

MAXIMUM 1.750 IN.

RECOMMENDED
WORKING STROKE
0.625 IN. TO 0.9 IN.
NOM 0.750 IN.

INTERNAL STOPS 1.9 IN.

2120647.11
5/20/93

A-20

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 22 - SPEED SENSOR
A

ON HIGHWAY
TRANSMISSION

OFF-HIGHWAY
TRANSMISSION
CHASSIS HARNESS
SPEED SENSOR

SPEED SENSOR CONNECTOR

CHASSIS WIRING HARNESS
CHASSIS CONNECTOR
SPEED SENSOR
ON HIGHWAY
115-165
A
B
OFF HIGHWAY
50-200

J1A
BLACK
WHITE
BLACK
GND

113
112
106A

1M
1L
1N

ECU
J1B

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-22

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 23 - PRIMARY SHIFT SELECTOR

SHIFT SELECTOR,
PUSH BUTTON
CAB HARNESS,
LEVER SHIFT
SELECTOR CONNECTOR

SHIFT SELECTOR, LEVER

CAB HARNESS,
PUSH BUTTON SHIFT
SELECTOR CONNECTOR

SHIFT SELECTOR CONNECTOR, LEVER TYPE

J1B

VEHICLE
INTERFACE
CONNECTIONS

12V LAMP BGND

234
24V GND
12V LAMP AGND
230
24V DIM
235
24V IGN
225
12V IGN
233
12V DIM
231
N.STRT
223B
RED

BLK

SHIFT
SELECTOR
14-3F** 11-3A

YEL
WHI
YEL
BLU
12V
12V

10-1F
15-2A
12-1C
13-2F
9-1A
8-1D

2-1B
3-2A
4-3B
5-1E
6-2E
7-3E
1-3C

RED
212

O.N. SHIFT

204
221
206
220
218
219
210A

WHI
VIO
VIO
YEL
BLU
GRN
BLK

S.S.1
S.S.2
S.S.4
S.S.8
S.S.PAR
S.S.DV
ECU
GND

*PUSH BUTTON TERMINALS

**LEVER SELECTOR TERMINALS

A-24

COPYRIGHT 1994 GENERAL MOTORS CORP.

3J
1F
2F
1G
2G
1H
2H
2C

J1A

ECU

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 23 - PRIMARY SHIFT SELECTOR

J1A CONNECTOR

J1A CAB
HARNESS

ECU

A-26

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 24 - TRANSMISSION OIL TEMPERATURE

CHASSIS HARNESS
LOCKUP VALVE BODY
CONNECTOR

BULKHEAD
CONNECTOR
CHASSIS HARNESS
CONNECTOR

5/6/8/9000 SERIES
OFF-HIGHWAY TRANSMISSION
LOCKUP SOLENOID/TEMP SENSOR
HARNESS CONNECTOR

ON HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
+A
P

I
N
T
E
R
N
A
L
W
I
R
I
N
G

B
U
L
K
H
E
A
D

123
106B

VIOLET
BLACK

2L
1N

J1B

C
O
N
N
E
C
T
O
R

OFF HIGHWAY
J1A
LOCATION LOCK-UP VALVE BODY

ECU
+C
D

I
N
T
E
R
N
A
L

5K TO 130K

103
106B

VIOLET
BLACK

2L
1N

J1B

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
5K TO 130K

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-28

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 24 - TRANSMISSION OIL TEMPERATURE
Temperature Sensor Plot
Resistance vs Temperature Characteristics for Oil Temperature Sensor

1000
900
800
700
600
500
400
300

RESISTANCE (K

200

100
90
80
70
60
50
40
30
20

10
9
8
7
6
5
4
3
2

1
-60

-30

30

60

90

120

150

180

210

TEMPERATURE (F)

A-30

COPYRIGHT 1994 GENERAL MOTORS CORP.

240

270

300

330

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 31 - SECONDARY SHIFT SELECTOR

SECONDARY HARNESS,
SELECTOR, LEVER

SHIFT SELECTOR,
PUSH BUTTON
SHIFT SELECTOR, LEVER

SECONDARY HARNESS,
SHIFT SELECTOR,
PUSH BUTTON

SHIFT SELECTOR
CONNECTOR,
PUSH BUTTON

SHIFT SELECTOR CONNECTOR,

LEVER TYPE

ECU
SELECTOR
J13
SECONDARY
MODE
CONNECTOR

301

RED

D.N. SHIFT

11-3A

14-3F

319

BLK

302
303*
304
305*
306
307
308

GRN
VIO
YEL
YEL
VIO
BLU
BLK

S.S DV
S.S. 2
S.S. 8
S.S. 1
S.S. 4
S.S. PAR
ECU GND

7-3E
3-2B
5-1E
2-1B
4-3B
6-2E
1-3C

10-1F
15-2A
12-1C
13-2F
9-1A
8-1D

317
324
321
318
322
323

WHT
WHT
VIO
VIO
BLU
RED

P.B.-LVR

A-32

COPYRIGHT 1994 GENERAL MOTORS CORP.

12V LMP B GND

24V LMP GND
12V LMP A GND
24V DIM
24V IGN
12V IGN
12V LMP DIM
NEUT STRT
ECU PWR

VEHICLE
INTERFACE
CONNECTIONS

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 31 - SECONDARY SHIFT SELECTOR

J3 SECONDARY MODE
CONNECTOR

J3 SECONDARY CONNECTOR

A-34

COPYRIGHT 1994 GENERAL MOTORS CORP.

ECU

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 32 - WRONG DIRECTION SIGNAL (ON-HIGHWAY ONLY)

J1A
LOCATION-VALVE BODY

ECU
E
F
G

CHASSIS WIRING
HARNESS CONNECTOR

RED
BLUE
YELLOW

101
118
116

+2N
3P
1R

J1B

FWD
REV

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-36

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 32 - WRONG DIRECTION SIGNAL (ON-HIGHWAY ONLY)

ECU

J1B CHASSIS HARNESS

J1B CONNECTOR

A-38

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 33 - TEMPERATURE SENSOR

CHASSIS HARNESS
LOCKUP VALVE BODY
CONNECTOR

BULKHEAD
CONNECTOR
CHASSIS HARNESS
CONNECTOR

5/6/8/9000 SERIES
OFF-HIGHWAY TRANSMISSION
LOCKUP SOLENOID/TEMP SENSOR
HARNESS CONNECTOR

ON HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
+A
P

I
N
T
E
R
N
A
L
W
I
R
I
N
G

B
U
L
K
H
E
A
D

123
106B

VIOLET
BLACK

2L
1N

J1B

C
O
N
N
E
C
T
O
R

OFF HIGHWAY
J1A
LOCATION LOCK-UP VALVE BODY

ECU
+C
D

I
N
T
E
R
N
A
L

5K TO 130K

103
106B

VIOLET
BLACK

2L
1N

J1B

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
5K TO 130K

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-40

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 33 - TEMPERATURE SENSOR
This code means that the ECU has received signals that the transmission oil temperature is either too hot or too
cold. This code is set if the oil temperature is greater than 350 degrees F (204 C) or below -100 degrees F (-73 C).
Code 33 may sometimes erase a previously set Code 24.
NOTE:

All temperatures stated here are subject to PROM calibration.

Some potential non-electronic control causes include:

Elevated transmission oil temperature caused by restricted flow through the oil cooler circuit, internal
component failure, etc.
An overheating engine.
Check these items and make repairs as needed before troubleshooting the electronic control.
Some potential electronic control causes include:
Opens or shorts in on-highway chassis harness wires 123 and 106B.
Opens or shorts in off-highway chassis harness wires 103 and 106B.
Opens or shorts in the on-highway electro-hydraulic valve body circuit between terminals A and P.
Opens or shorts in the off-highway electro-hydraulic valve body circuit between terminals C and D.
Faulty temperature sensor.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the chassis wiring harness for opens and shorts.
a. For on-highway transmissions, remove the J1B connector from the ECU and remove the bulkhead
connector from the transmission. Check wires 123 and 106B for opens, shorts to each other, shorts to
other wires and shorts to ground.
b. For off-highway transmissions, remove the J1B connector from the ECU and remove the chassis harness
connector from the lockup valve body. Check wires 103 and 106B for opens, shorts to each other, shorts
to other wires and shorts to ground.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-41

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 33 - TEMPERATURE SENSOR
Temperature Sensor Plot
Resistance vs Temperature Characteristics for Oil Temperature Sensor

1000
900
800
700
600
500
400
300

RESISTANCE (K

200

100
90
80
70
60
50
40
30
20

10
9
8
7
6
5
4
3
2

1
-60

-30

30

60

90

120

150

180

210

TEMPERATURE (F)

A-42

COPYRIGHT 1994 GENERAL MOTORS CORP.

240

270

300

330

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 33 - TEMPERATURE SENSOR
2. If the chassis wiring harness is okay, check the temperature sensor.
a. For on-highway transmissions, check resistance between bulkhead terminals A and P. Check temperature
sensor resistance at varying sump temperatures. Resistance should always be between 5000 and
130,000 ohms.
b. For off-highway transmissions, check resistance between lockup valve body terminals C and D. Check
temperature sensor resistance at varying sump temperatures. Resistance should always be between 5000
and 130,000 ohms.
3. If the chassis wiring harness and temperature sensor are okay, and transmission sump oil temperatures are
within normal operating limits, replace the ECU. If replacing the ECU fixes the problem, verify the old ECU
is bad by reinstalling it, road testing the vehicle, and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-43

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 34 - PROM CHECK

ONLY AUTHORIZED WARRANTY OUTLETS

ARE PERMITTED TO OPEN THE PROM
ACCESS COVER. WARRANTY MAY BE VOID
IF OPENED BY UNAUTHORIZED PERSONNEL.

CAUTION: If the PROM removal tool is not used, the socket in the ECU can be damaged and an ECU
replacement would be required.
Using PROM removal tool J 35889-A, the retainer and PROM should lift easily from the PROM socket.
Tool J 35889-A is available in every service PROM kit.
Engage one end of the PROM retainer with the hook end of the tool.
Press on the vertical bar end of the tool and rock the engaged end of the PROM retainer up as far
as possible.
Engage the opposite end of the PROM retainer in the same manner and rock this end up as far as possible.
Repeat this procedure until the PROM retainer and PROM are free of the PROM socket.

A-44

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 34 - PROM CHECK
This code means that the ECU has sensed a problem with the PROM.
Some potential causes include:
Faulty PROM.
Improperly installed PROM.
Mis-matched PROM and ECU.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Make sure the PROM is properly installed.
a. Make sure the PROM is properly indexed.
b. Make sure the PROM is fully seated in the ECUs socket.
2. If the PROM is properly installed, use ECIS to ensure the PROM is correct for the ECU and
vehicle application.
3. If the PROM is properly installed and correct for the application, replace the PROM. If replacing the PROM
fixes the problem, verify the old PROM is bad by reinstalling it, road testing the vehicle, and checking
for codes.
4. If the problem still exists, replace the ECU. If replacing the ECU fixes the problem, verify the old ECU is
bad by reinstalling it, road testing the vehicle, and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-45

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 41 - J SOLENOID (ON-HIGHWAY), A SOLENOID (OFF-HIGHWAY)

HARNESS CONNECTOR
MAIN VALVE BODY

CHASSIS HARNESS\
MAIN VALVE BODY

BULKHEAD
CONNECTOR
CHASSIS HARNESS
CONNECTOR

OFF-HIGHWAY
TRANSMISSION
VALVE BODY CONNECTOR

ON HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
D
B

I
N
T
E
R
N
A
L
W
I
R
I
N
G

B
U
L
K
H
E
A
D

C
O
N
N
E
C
T
O
R

111
114

GREEN
WHITE

3M
3L

J1B

OFF HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
A
B

I
N
T
E
R
N
A
L

J SOL 9-20

115
116

GREEN
YELLOW

3M
3L

J1B

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
A SOL 12-24

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-46

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 41 - J SOLENOID (ON-HIGHWAY), A SOLENOID (OFF-HIGHWAY)
This code means that the ECU has received improper signals from the J solenoid circuit (on-highway) or A
solenoid circuit (off-highway). Solenoid J (on-highway) controls the flow of main pressure to the top of the
neutral-range valve. Solenoid A (off-highway) controls the flow of main pressure under the 1-2 shift valve during
lock-in-range electrical failure.
Some potential causes include:
Opens or shorts in on-highway chassis harness wires 111 and 114.
Opens or shorts in off-highway chassis harness wires 115 and 116.
Opens or shorts in the on-highway electro-hydraulic valve body circuit between terminals D and B.
Opens or shorts in the off-highway electro-hydraulic valve body circuit between terminals A and B.
Faulty solenoid(s).
Problems with related solenoid circuits.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the solenoid circuits resistance.
a. Remove the J1B connector from the ECU.
b. For on-highway transmissions, connect ohmmeter leads to J1B terminals 3M and 3L. J solenoid circuit
resistance should be between 9 and 20 ohms.
c. For off-highway transmissions, connect ohmmeter leads to J1B terminals 3M and 3L. A solenoid circuit
resistance should be between 12 and 24 ohms.
If readings are correct, proceed to Troubleshooting Step 4.
2. If resistance readings are incorrect, check the chassis wiring harness.
a. Remove the J1B connector from the ECU, and remove the bulkhead connector from the transmission.
b. For on-highway transmissions, check wires 111 and 114 for opens, shorts to each other, shorts to other
wires and shorts to ground.
c. For off-highway transmissions, check wires 115 and 116 for opens, shorts to each other, shorts to other
wires and shorts to ground.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-47

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 41 - J SOLENOID (ON-HIGHWAY), A SOLENOID (OFF-HIGHWAY)

ON HIGHWAY

BULKHEAD CONNECTOR

MAIN VALVE BODY

CONNECTOR

B
C

OFF HIGHWAY

E
F
SOLENOID AND COVER
ASSEMBLY

A-48

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 41 - J SOLENOID (ON-HIGHWAY), A SOLENOID (OFF-HIGHWAY)
3. If the chassis wiring harness is okay, check the internal components and circuits.
a. For on-highway transmissions, check resistance between bulkhead terminals D and B. Resistance should
be between 9 and 20 ohms.
b. For off-highway transmissions, check resistance between bulkhead terminals A and B. Resistance should
be between 12 and 24 ohms.
c. If resistance readings are incorrect, determine whether the problem is in the internal wiring harness
or the solenoid.
1) Remove the electrical connector from solenoid J (on-highway) or solenoid A (off-highway).
2) Use an ohmmeter to check the solenoids internal resistance.
3) If solenoid resistance is incorrect, replace the solenoid.
4) If solenoid resistance is okay (9-20 ohms for on-highway, 12-24 ohms for off-highway), check the
solenoid circuits internal wiring harness wires for opens, shorts to each other, shorts to other wires
and shorts to ground. Isolate and repair problems as needed.
4. If the solenoids circuit resistance is okay, check related solenoid circuits for problems.
a. Refer to Troubleshooting Steps for Codes 42, 43, 44, 45 and 46. Isolate and repair problems as needed.
5. If the solenoids circuit resistance is okay, and related solenoid circuits are okay, replace the ECU. If
replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it, road testing the vehicle,
and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-49

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 42 - F SOLENOID (ON-HIGHWAY), B SOLENOID (OFF-HIGHWAY)

HARNESS CONNECTOR
MAIN VALVE BODY

CHASSIS HARNESS\
MAIN VALVE BODY

BULKHEAD
CONNECTOR
CHASSIS HARNESS
CONNECTOR

OFF-HIGHWAY
TRANSMISSION
VALVE BODY CONNECTOR

ON HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
V
U

I
N
T
E
R
N
A
L
W
I
R
I
N
G

B
U
L
K
H
E
A
D

120
105

BLUE
VIOLET

2T
1W

J1B

C
O
N
N
E
C
T
O
R

OFF HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
D
C

I
N
T
E
R
N
A
L

J SOL 9-20

117
114

BLACK
WHITE

2T
1W

J1B

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
A SOL 12-24

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-50

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 42 - F SOLENOID (ON-HIGHWAY), B SOLENOID (OFF-HIGHWAY)
This code means that the ECU has received improper signals from the F solenoid circuit (on-highway) or B
solenoid circuit (off-highway). Solenoid F (on-highway) controls main pressure flow to the bottom of the
forward-reverse valve. Solenoid B (off-highway) controls the reverse shift valve.
Some potential causes include:
Opens or shorts in on-highway chassis harness wires 120 and 105.
Opens or shorts in off-highway chassis harness wires 117 and 114.
Opens or shorts in the on-highway electro-hydraulic valve body circuit between terminals V and U.
Opens or shorts in the off-highway electro-hydraulic valve body circuit between terminals D and C.
Faulty solenoid(s).
Problems with related solenoid circuits.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the solenoid circuits resistance.
a. Remove the J1B connector from the ECU.
b. For on-highway transmissions, connect ohmmeter leads to J1B terminals 2T and 1W. F solenoid circuit
resistance should be between 9 and 20 ohms.
c. For off-highway transmissions, connect ohmmeter leads to J1B terminals 2T and 1W. B solenoid circuit
resistance should be between 12 and 24 ohms.
If readings are correct, proceed to Troubleshooting Step 4.
2. If resistance readings are incorrect, check the chassis wiring harness.
a. Remove the J1B connector from the ECU, and remove the bulkhead connector from the transmission.
b. For on-highway transmissions, check wires 120 and 105 for opens, shorts to each other, shorts to other
wires and shorts to ground.
c. For off-highway transmissions, check wires 117 and 114 for opens, shorts to each other, shorts to other
wires and shorts to ground.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-51

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 42 - F SOLENOID (ON-HIGHWAY), B SOLENOID (OFF-HIGHWAY)

ON HIGHWAY

BULKHEAD CONNECTOR

MAIN VALVE BODY

CONNECTOR

B
C

OFF HIGHWAY

E
F
SOLENOID AND COVER
ASSEMBLY

A-52

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 42 - F SOLENOID (ON-HIGHWAY), B SOLENOID (OFF-HIGHWAY)
3. If the chassis wiring harness is okay, check the internal components and circuits.
a. For on-highway transmissions, check resistance between bulkhead terminals V and U. Resistance should
be between 9 and 20 ohms.
b. For off-highway transmissions, check resistance between bulkhead terminals D and C. Resistance should
be between 12 and 24 ohms.
c. If resistance readings are incorrect, determine whether the problem is in the internal wiring harness
or the solenoid.
1) Remove the electrical connector from solenoid F (on-highway) or solenoid B (off-highway).
2) Use an ohmmeter to check the solenoids internal resistance.
3) If solenoid resistance is incorrect, replace the solenoid.
4) If solenoid resistance is okay (9-20 ohms for on-highway, 12-24 ohms for off-highway), check the
solenoid circuits internal wiring harness wires for opens, shorts to each other, shorts to other wires
and shorts to ground. Isolate and repair problems as needed.
4. If the solenoids circuit resistance is okay, check related solenoid circuits for problems.
a. Refer to Troubleshooting Steps for Codes 41, 43, 44, 45 and 46. Isolate and repair problems as needed.
5. If the solenoids circuit resistance is okay, and related solenoid circuits are okay, replace the ECU. If
replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it, road testing the vehicle,
and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-53

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 43 - D SOLENOID (ON-HIGHWAY), C SOLENOID (OFF-HIGHWAY)

HARNESS CONNECTOR
MAIN VALVE BODY

CHASSIS HARNESS\
MAIN VALVE BODY

BULKHEAD
CONNECTOR
CHASSIS HARNESS
CONNECTOR

OFF-HIGHWAY
TRANSMISSION
VALVE BODY CONNECTOR

ON HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
W
V

I
N
T
E
R
N
A
L
W
I
R
I
N
G

B
U
L
K
H
E
A
D

C
O
N
N
E
C
T
O
R

110
120

WHITE
BLUE

1S
2T

J1B

OFF HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
N
D

I
N
T
E
R
N
A
L

D SOL 9-20

109
117

BLUE
BLACK

1S
2T

J1B

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
C SOL 12-24

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-54

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 43 - D SOLENOID (ON-HIGHWAY), C SOLENOID (OFF-HIGHWAY)
This code means that the ECU has received improper signals from the D solenoid circuit (on-highway) or C
solenoid circuit (off-highway). Solenoid D (on-highway) controls the 3-4 shift valve. Solenoid C (off-highway)
controls the 1-2 shift valve.
Some potential causes include:
Opens or shorts in on-highway chassis harness wires 110 and 120.
Opens or shorts in off-highway chassis harness wires 109 and 117.
Opens or shorts in the on-highway electro-hydraulic valve body circuit between terminals W and V.
Opens or shorts in the off-highway electro-hydraulic valve body circuit between terminals N and D.
Faulty solenoid(s).
Problems with related solenoid circuits.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the solenoid circuits resistance.
a. Remove the J1B connector from the ECU.
b. For on-highway transmissions, connect ohmmeter leads to J1B terminals 1S and 2T. D solenoid circuit
resistance should be between 9 and 20 ohms.
c. For off-highway transmissions, connect ohmmeter leads to J1B terminals 1S and 2T. C solenoid circuit
resistance should be between 12 and 24 ohms.
If readings are correct, proceed to Troubleshooting Step 4.
2. If resistance readings are incorrect, check the chassis wiring harness.
a. Remove the J1B connector from the ECU, and remove the bulkhead connector from the transmission.
b. For on-highway transmissions, check wires 110 and 120 for opens, shorts to each other, shorts to other
wires and shorts to ground.
c. For off-highway transmissions, check wires 109 and 117 for opens, shorts to each other, shorts to other
wires and shorts to ground.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-55

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 43 - D SOLENOID (ON-HIGHWAY), C SOLENOID (OFF-HIGHWAY)

ON HIGHWAY

BULKHEAD CONNECTOR

MAIN VALVE BODY

CONNECTOR

B
C

OFF HIGHWAY

E
F
SOLENOID AND COVER
ASSEMBLY

A-56

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 43 - D SOLENOID (ON-HIGHWAY), C SOLENOID (OFF-HIGHWAY)
3. If the chassis wiring harness is okay, check the internal components and circuits.
a. For on-highway transmissions, check resistance between bulkhead terminals W and V. Resistance should
be between 9 and 20 ohms.
b. For off-highway transmissions, check resistance between bulkhead terminals N and D. Resistance should
be between 12 and 24 ohms.
c. If resistance readings are incorrect, determine whether the problem is in the internal wiring harness
or the solenoid.
1) Remove the electrical connector from solenoid D (on-highway) or solenoid C (off-highway).
2) Use an ohmmeter to check the solenoids internal resistance.
3) If solenoid resistance is incorrect, replace the solenoid.
4) If solenoid resistance is okay (9-20 ohms for on-highway, 12-24 ohms for off-highway), check the
solenoid circuits internal wiring harness wires for opens, shorts to each other, shorts to other wires
and shorts to ground. Isolate and repair problems as needed.
4. If the solenoids circuit resistance is okay, check related solenoid circuits for problems.
a. Refer to Troubleshooting Steps for Codes 41, 42, 44, 45 and 46. Isolate and repair problems as needed.
5. If the solenoids circuit resistance is okay, and related solenoid circuits are okay, replace the ECU. If
replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it, road testing the vehicle,
and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-57

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 44 - C SOLENOID (ON-HIGHWAY), D SOLENOID (OFF-HIGHWAY)

HARNESS CONNECTOR
MAIN VALVE BODY

CHASSIS HARNESS\
MAIN VALVE BODY

BULKHEAD
CONNECTOR
CHASSIS HARNESS
CONNECTOR

OFF-HIGHWAY
TRANSMISSION
VALVE BODY CONNECTOR

ON HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
B
W

I
N
T
E
R
N
A
L
W
I
R
I
N
G

B
U
L
K
H
E
A
D

114
110

WHITE
WHITE

3L
1S

J1B

C
O
N
N
E
C
T
O
R

OFF HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
B
N

I
N
T
E
R
N
A
L

C SOL 9-20

116
109

YELLOW
BLUE

3L
1S

J1B

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
D SOL 12-24

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-58

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 44 - C SOLENOID (ON-HIGHWAY), D SOLENOID (OFF-HIGHWAY)
This code means that the ECU has received improper signals from the C solenoid circuit (on-highway) or D
solenoid circuit (off-highway). Solenoid C (on-highway) controls the 2-3 shift valve. Solenoid D (off-highway)
controls the 3-4 shift valve.
Some potential causes include:
Opens or shorts in on-highway chassis harness wires 114 and 110.
Opens or shorts in off-highway chassis harness wires 116 and 109.
Opens or shorts in the on-highway electro-hydraulic valve body circuit between terminals B and W.
Opens or shorts in the off-highway electro-hydraulic valve body circuit between terminals B and N.
Faulty solenoid(s).
Problems with related solenoid circuits.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the solenoid circuits resistance.
a. Remove the J1B connector from the ECU.
b. For on-highway transmissions, connect ohmmeter leads to J1B terminals 3L and 1S. C solenoid circuit
resistance should be between 9 and 20 ohms.
c. For off-highway transmissions, connect ohmmeter leads to J1B terminals 3L and 1S. D solenoid circuit
resistance should be between 12 and 24 ohms.
If readings are correct, proceed to Troubleshooting Step 4.
2. If resistance readings are incorrect, check the chassis wiring harness.
a. Remove the J1B connector from the ECU, and remove the bulkhead connector from the transmission.
b. For on-highway transmissions, check wires 114 and 110 for opens, shorts to each other, shorts to other
wires and shorts to ground.
c. For off-highway transmissions, check wires 116 and 109 for opens, shorts to each other, shorts to other
wires and shorts to ground.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-59

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 44 - C SOLENOID (ON-HIGHWAY), D SOLENOID (OFF-HIGHWAY)

ON HIGHWAY

BULKHEAD CONNECTOR

MAIN VALVE BODY

CONNECTOR

B
C

OFF HIGHWAY

E
F
SOLENOID AND COVER
ASSEMBLY

A-60

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 44 - C SOLENOID (ON-HIGHWAY), D SOLENOID (OFF-HIGHWAY)
3. If the chassis wiring harness is okay, check the internal components and circuits.
a. For on-highway transmissions, check resistance between bulkhead terminals B and W. Resistance should
be between 9 and 20 ohms.
b. For off-highway transmissions, check resistance between bulkhead terminals B and N. Resistance should
be between 12 and 24 ohms.
c. If resistance readings are incorrect, determine whether the problem is in the internal wiring harness
or the solenoid.
1) Remove the electrical connector from solenoid C (on-highway) or solenoid D (off-highway).
2) Use an ohmmeter to check the solenoids internal resistance.
3) If solenoid resistance is incorrect, replace the solenoid.
4) If solenoid resistance is okay (9-20 ohms for on-highway, 12-24 ohms for off-highway), check the
solenoid circuits internal wiring harness wires for opens, shorts to each other, shorts to other wires
and shorts to ground. Isolate and repair problems as needed.
4. If the solenoids circuit resistance is okay, check related solenoid circuits for problems.
a. Refer to Troubleshooting Steps for Codes 41, 42, 43, 45 and 46. Isolate and repair problems as needed.
5. If the solenoids circuit resistance is okay, and related solenoid circuits are okay, replace the ECU. If
replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it, road testing the vehicle,
and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-61

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 45 - B SOLENOID (ON-HIGHWAY), E SOLENOID (OFF-HIGHWAY)

HARNESS CONNECTOR
MAIN VALVE BODY

CHASSIS HARNESS\
MAIN VALVE BODY

BULKHEAD
CONNECTOR
CHASSIS HARNESS
CONNECTOR

OFF-HIGHWAY
TRANSMISSION
VALVE BODY CONNECTOR

ON HIGHWAY
J1A
LOCATION-VALVE BODY

I
N
T
E
R
N
A
L
W
I
R
I
N
G

B
U
L
K
H
E
A
D

ECU
C
O
N
N
E
C
T
O
R

U
T

105
115

VIOLET
GREEN

121

RED

1W
1T

J1B

(5 SPEED)

3T
(4 SPEED)

OFF HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
C
K

I
N
T
E
R
N
A
L

B SOL 9-20

114
108

WHITE
YELLOW

1W
3T

J1B

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
E SOL 12-24

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-62

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 45 - B SOLENOID (ON-HIGHWAY), E SOLENOID (OFF-HIGHWAY)
This code means that the ECU has received improper signals from the B solenoid circuit (on-highway) or E
solenoid circuit (off-highway). Solenoid B (on-highway) controls the 1-2 shift valve. Solenoid E (off-highway)
controls the 5-6 shift valve.
Some potential causes include:
Opens or shorts in on-highway chassis harness wires 105 and 115 (five speed models), or 105 and 121
(four speeds).
Opens or shorts in off-highway chassis harness wires 114 and 108.
Opens or shorts in the on-highway electro-hydraulic valve body circuit between terminals U and T (five
speed models), or U and C (four speeds).
Opens or shorts in the off-highway electro-hydraulic valve body circuit between terminals C and K.
Faulty solenoid(s).
Problems with related solenoid circuits.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the solenoid circuits resistance.
a. Remove the J1B connector from the ECU.
b. For on-highway transmissions, connect ohmmeter leads to J1B terminals 1W and 1T (five speed models)
or terminals 1W and 3T (four speed models). B solenoid circuit resistance should be between 9
and 20 ohms.
c. For off-highway transmissions, connect ohmmeter leads to J1B terminals 1W and 3T. E solenoid circuit
resistance should be between 12 and 24 ohms.
If readings are correct, proceed to Troubleshooting Step 4.
2. If resistance readings are incorrect, check the chassis wiring harness.
a. Remove the J1B connector from the ECU, and remove the bulkhead connector from the transmission.
b. For on-highway transmissions, check wires 105 and 115 (five speed models) or 105 and 121 (four speed
models) for opens, shorts to each other, shorts to other wires and shorts to ground.
c. For off-highway transmissions, check wires 114 and 108 for opens, shorts to each other, shorts to other
wires and shorts to ground.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-63

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 45 - B SOLENOID (ON-HIGHWAY), E SOLENOID (OFF-HIGHWAY)

ON HIGHWAY

BULKHEAD CONNECTOR

MAIN VALVE BODY

CONNECTOR

B
C

OFF HIGHWAY

E
F
SOLENOID AND COVER
ASSEMBLY

A-64

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 45 - B SOLENOID (ON-HIGHWAY), E SOLENOID (OFF-HIGHWAY)
3. If the chassis wiring harness is okay, check the internal components and circuits.
a. For on-highway transmissions, check resistance between bulkhead terminals U and T (five speed models)
or U and C (four speed models). Resistance should be between 9 and 20 ohms.
b. For off-highway transmissions, check resistance between bulkhead terminals C and K. Resistance should
be between 12 and 24 ohms.
c. If resistance readings are incorrect, determine whether the problem is in the internal wiring harness
or the solenoid.
1) Remove the electrical connector from solenoid B (on-highway) or solenoid E (off-highway).
2) Use an ohmmeter to check the solenoids internal resistance.
3) If solenoid resistance is incorrect, replace the solenoid.
4) If solenoid resistance is okay (9-20 ohms for on-highway, 12-24 ohms for off-highway), check the
solenoid circuits internal wiring harness wires for opens, shorts to each other, shorts to other wires
and shorts to ground. Isolate and repair problems as needed.
4. If the solenoids circuit resistance is okay, check related solenoid circuits for problems.
a. Refer to Troubleshooting Steps for Codes 41, 42, 43, 44 and 46. Isolate and repair problems as needed.
5. If the solenoids circuit resistance is okay, and related solenoid circuits are okay, replace the ECU. If
replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it, road testing the vehicle,
and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-65

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 46 - A SOLENOID (ON-HIGHWAY ONLY)

BULKHEAD
CONNECTOR
CHASSIS HARNESS
CONNECTOR

J1A
LOCATION-VALVE BODY

ECU
T
C

I
N
T
E
R
N
A
L

B
U
L
K
H
E
A
D

115
121

GREEN
RED

1T
3T

J1B

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
A SOL 9-20

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-66

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 46 - A SOLENOID (ON-HIGHWAY ONLY)
This code means that the ECU has received improper signals from the A solenoid circuit. Solenoid A controls the
low-1 shift valve.
Some potential causes include:
Opens or shorts in chassis harness wires 115 and 121.
Opens or shorts in the electro-hydraulic valve body circuit between terminals T and C.
Faulty solenoid.
Problems with related solenoid circuits.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the solenoid circuits resistance.
a. Remove the J1B connector from the ECU.
b. Connect ohmmeter leads to J1B terminals 1T and 3T. Solenoid circuit resistance should be between 9 and
20 ohms.
If readings are correct, proceed to Troubleshooting Step 4.
2. If resistance readings are incorrect, check the chassis wiring harness.
a. Remove the J1B connector from the ECU, and remove the bulkhead connector from the transmission.
b. Check wires 115 and 121 for opens, shorts to each other, shorts to other wires and shorts to ground.
Isolate and repair problems as needed.
3. If the chassis wiring harness is okay, check the internal components and circuits.
a. Check resistance between bulkhead terminals T and C. Resistance should be between 9 and 20 ohms.
b. If resistance readings are incorrect, determine whether the problem is in the internal wiring harness
or the solenoid.
1) Remove the electrical connector from solenoid A.
2) Use an ohmmeter to check the solenoids internal resistance.
3) If resistance is incorrect, replace the solenoid.
4) If solenoid resistance is okay (9-20 ohms), check the solenoid circuits internal wiring harness wires
for opens, shorts to each other, shorts to other wires and shorts to ground. Isolate and repair problems
as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-67

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 46 - A SOLENOID (ON-HIGHWAY ONLY)

BULKHEAD CONNECTOR

A-68

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 46 - A SOLENOID (ON-HIGHWAY ONLY)
4. If the solenoids circuit resistance is okay, check related solenoid circuits for problems.
a. Refer to Troubleshooting Steps for Codes 41, 42, 43, 44 and 45. Isolate and repair problems as needed.
5. If the solenoids circuit resistance is okay, and related solenoid circuits are okay, replace the ECU. If
replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it, road testing the vehicle,
and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-69

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 51 - G SOLENOID (ON-HIGHWAY), K SOLENOID (OFF-HIGHWAY)

D
C

A
B

CHASSIS HARNESS
LOCKUP VALVE BODY
CHASSIS HARNESS
CONNECTOR

5/6/8/9000 SERIES
OFF-HIGHWAY TRANSMISSION

LOCKUP SOLENOID/TWMP
SENSOR HARNESS CONNECTOR

ON HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
O
L

I
N
T
E
R
N
A
L
W
I
R
I
N
G

B
U
L
K
H
E
A
D

107
109

GREEN
BLUE

1Y
2Y

J1B

C
O
N
N
E
C
T
O
R

OFF HIGHWAY
J1A
LOCATION-LOCKUP VALVE BODY

ECU
B
A

I
N
T
E
R
N
A
L

G SOL 9-20

102
101

GREEN
RED

1Y
2Y

J1B

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
K SOL 12-24

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-70

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 51 - G SOLENOID (ON-HIGHWAY), K SOLENOID (OFF-HIGHWAY)
This code means that the ECU has received improper signals from the G solenoid circuit (on-highway) or K
solenoid circuit (off-highway). Solenoid G (on-highway) controls the lockup relay valve. Solenoid K (offhighway) controls the lockup shift valve.
Some potential causes include:
Opens or shorts in on-highway chassis harness wires 107 and 109.
Opens or shorts in off-highway chassis harness wires 102 and 101.
Opens or shorts in the on-highway electro-hydraulic valve body circuit between terminals O and L.
Opens or shorts in the off-highway lockup valve body circuit between terminals B and A.
Faulty solenoid.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the solenoid circuits resistance.
a. Remove the J1B connector from the ECU.
b. For on-highway transmissions, connect ohmmeter leads to J1B terminals 1Y and 2Y. G solenoid circuit
resistance should be between 9 and 20 ohms.
c. For off-highway transmissions, connect ohmmeter leads to J1B terminals 1Y and 2Y. K solenoid circuit
resistance should be between 12 and 24 ohms.
If readings are correct, proceed to Troubleshooting Step 4.
2. If resistance readings are incorrect, check the chassis wiring harness.
a. Remove the J1B connector from the ECU, and remove the bulkhead connector from the transmission
(on-highway), or remove the lockup valve body connector from the lock-up valve body (off-highway).
b. For on-highway transmissions, check wires 107 and 109 for opens, shorts to each other, shorts to other
wires and shorts to ground.
c. For off-highway transmissions, check wires 102 and 101 for opens, shorts to each other, shorts to other
wires and shorts to ground.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-71

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 51 - G SOLENOID (ON-HIGHWAY), K SOLENOID (OFF-HIGHWAY)

ON HIGHWAY

BULKHEAD CONNECTOR

OFF HIGHWAY

LOCKUP SOLENOID/TEMP SENSOR

HARNESS CONNECTOR

A-72

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 51 - G SOLENOID (ON-HIGHWAY), K SOLENOID (OFF-HIGHWAY)
3. If the chassis wiring harness is okay, check the internal components and circuits.
a. For on-highway transmissions, check resistance between bulkhead terminals O and L. Resistance should
be between 9 and 20 ohms.
b. For off-highway transmissions, check resistance between lockup valve body terminals B and A.
Resistance should be between 12 and 24 ohms.
c. If resistance readings are incorrect, determine whether the problem is in the internal wiring harness
or the solenoid.
1) Remove the electrical connector from solenoid G (on-highway) or solenoid K (off-highway).
2) Use an ohmmeter to check the solenoids internal resistance.
3) If solenoid resistance is incorrect, replace the solenoid.
4) If solenoid resistance is okay (9-20 ohms for on-highway, 12-24 ohms for off-highway), check the
solenoid circuits internal wiring harness wires for opens, shorts to each other, shorts to other wires
and shorts to ground. Isolate and repair problems as needed.
4. If the solenoids circuit resistance is okay, replace the ECU. If replacing the ECU fixes the problem, verify
the old ECU is bad by reinstalling it, road testing the vehicle, and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-73

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 52 - E SOLENOID (ON-HIGHWAY), H OR J SOLENOID (OFF-HIGHWAY)

CHASSIS HARNESS,
1-2/T-B VALVE BODY CONNECTOR
BULKHEAD
CONNECTOR
CHASSIS HARNESS
CONNECTOR

1-2/T-B VALVE BODY

SOLENOID HARNESS
CONNECTOR

ON HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
M
N

I
N
T
E
R
N
A
L
W
I
R
I
N
G

B
U
L
K
H
E
A
D

C
O
N
N
E
C
T
O
R

119
117

RED
BLACK

2W
3Y

J1B

OFF HIGHWAY
J1A
LOCATION*

ECU
A
B

I
N
T
E
R
N
A
L

E SOL 9-20

C
O
N
N
E
C
T
O
R

125
105

WHT
VIO

2W
3Y

J1B

*CLBT 9681 Trim Boost

Valve Body
DP 8963

1-2 Shift
Valve Body

W
I
R
I
N
G
H - 8000
12-24
J - 9000

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-74

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 52 - E SOLENOID (ON-HIGHWAY), H OR J SOLENOID (OFF-HIGHWAY)
This code means that the ECU has received improper signals from the E solenoid circuit (on-highway) or the H or
J solenoid (off-highway). Solenoid E (on-highway) controls trimmer regulator valve operation. Solenoid H (offhighway) controls low range operation in DP 8000 series transmissions. Solenoid J controls trimmer regulator
operation in CLBT 9000 series transmissions.
Some potential causes include:
Opens or shorts in on-highway chassis harness wires 119 and 107.
Opens or shorts in off-highway chassis harness wires 125 and 105.
Opens or shorts in the on-highway electro-hydraulic valve body circuit between terminals M and N.
Opens or shorts in the off-highway low-low valve body circuit between terminals A and B.
Faulty solenoid(s).
Problems with related solenoid circuits.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the solenoid circuits resistance.
a. Remove the J1B connector from the ECU.
b. For on-highway transmissions, connect ohmmeter leads to J1B terminals 2W and 3Y. E solenoid circuit
resistance should be between 9 and 20 ohms.
c. For off-highway transmissions, connect ohmmeter leads to J1B terminals 2W and 3T. Solenoid circuit
resistance (for either solenoid H or J) should be between 12 and 24 ohms.
If readings are correct, proceed to Troubleshooting Step 4.
2. If resistance readings are incorrect, check the chassis wiring harness.
a. Remove the J1B connector from the ECU, and remove the bulkhead connector from the transmission
(on-highway), or remove the low-low valve body bulkhead connector from the low-low valve body
(off-highway).
b. For on-highway transmissions, check wires 119 and 117 for opens, shorts to each other, shorts to other
wires and shorts to ground.
c. For off-highway transmissions, check wires 125 and 105 for opens, shorts to each other, shorts to other
wires and shorts to ground.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-75

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 52 - E SOLENOID (ON-HIGHWAY), H OR J SOLENOID (OFF-HIGHWAY)

ON HIGHWAY

BULKHEAD CONNECTOR

OFF HIGHWAY

DP 8963 1-2 SHIFT

VALVE BODY

CLBT 9681 TRIM BOOST

VALVE BODY

A-76

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 52 - E SOLENOID (ON-HIGHWAY), H OR J SOLENOID (OFF-HIGHWAY)
3. If the chassis wiring harness is okay, check the internal components and circuits.
a. For on-highway transmissions, check resistance between bulkhead terminals M and N. Resistance should
be between 9 and 20 ohms.
b. For off-highway transmissions, check resistance between low-low valve body bulkhead terminals A and
B. Resistance should be between 12 and 24 ohms.
c. If resistance readings are incorrect, determine whether the problem is in the internal wiring harness
or the solenoid.
1) Remove the electrical connector from solenoid E (on-highway) or from solenoid H or J
(off-highway).
2) Use an ohmmeter to check the solenoids internal resistance.
3) If solenoid resistance is incorrect, replace the solenoid.
4) If solenoid resistance is okay (9-20 ohms for on-highway, 12-24 ohms for off-highway), check the
solenoid circuits internal wiring harness wires for opens, shorts to each other, shorts to other wires
and shorts to ground. Isolate and repair problems as needed.
4. If the solenoids circuit resistance is okay, check related solenoid circuits for problems.
a. Refer to Troubleshooting Steps for Code 53. Isolate and repair problems as needed.
5. If the solenoids circuit resistance is okay, and related solenoid circuits are okay, replace the ECU. If
replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it, road testing the vehicle,
and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-77

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 53 - H SOLENOID (ON-HIGHWAY), I SOLENOID (OFF-HIGHWAY)

CHASSIS HARNESS,
1-2/T-B VALVE BODY CONNECTOR
BULKHEAD
CONNECTOR
CHASSIS HARNESS
CONNECTOR

1-2/T-B VALVE BODY

SOLENOID HARNESS
CONNECTOR

ON HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
M
N

I
N
T
E
R
N
A
L
W
I
R
I
N
G

B
U
L
K
H
E
A
D

C
O
N
N
E
C
T
O
R

119
117

RED
BLACK

2W
3Y

J1B

OFF HIGHWAY
J1A
LOCATION*

ECU
A
B

I
N
T
E
R
N
A
L

E SOL 9-20

C
O
N
N
E
C
T
O
R

125
105

WHT
VIO

2W
3Y

J1B

*CLBT 9681 Trim Boost

Valve Body
DP 8963

1-2 Shift
Valve Body

W
I
R
I
N
G
H - 8000
12-24
J - 9000

ECU
J1B CHASSIS HARNESS

J1B CONNECTOR

A-78

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 53 - H SOLENOID (ON-HIGHWAY), I SOLENOID (OFF-HIGHWAY)
This code means that the ECU has received improper signals from the H solenoid circuit (on-highway) or the I
solenoid (off-highway). Solenoid H (on-highway) controls main pressure flow to the bottom of the neutral-range
valve. Solenoid I (off-highway) controls low range unlock operation in DP 8000 series transmissions.
Some potential causes include:
Opens or shorts in on-highway chassis harness wires 108 and 117.
Opens or shorts in off-highway chassis harness wires 107 and 105.
Opens or shorts in the on-highway electro-hydraulic valve body circuit between terminals K and N.
Opens or shorts in the off-highway low-low valve body circuit between terminals D and B.
Faulty solenoid(s).
Problems with related solenoid circuits.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the solenoid circuits resistance.
a. Remove the J1B connector from the ECU.
b. For on-highway transmissions, connect ohmmeter leads to J1B terminals 2M and 3Y. H solenoid circuit
resistance should be between 9 and 20 ohms.
c. For off-highway transmissions, connect ohmmeter leads to J1B terminals 2M and 3Y. I Solenoid circuit
resistance should be between 12 and 24 ohms.
If readings are correct, proceed to Troubleshooting Step 4.
2. If resistance readings are incorrect, check the chassis wiring harness.
a. Remove the J1B connector from the ECU, and remove the bulkhead connector from the transmission
(on-highway), or remove the low-low valve body bulkhead connector from the low-low valve body
(off-highway).
b. For on-highway transmissions, check wires 108 and 117 for opens, shorts to each other, shorts to other
wires and shorts to ground.
c. For off-highway transmissions, check wires 107 and 105 for opens, shorts to each other, shorts to other
wires and shorts to ground.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-79

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 53 - H SOLENOID (ON-HIGHWAY), I SOLENOID (OFF-HIGHWAY)

ON HIGHWAY

BULKHEAD CONNECTOR

OFF HIGHWAY

1-2 SHIFT VALVE

BODY ASSEMBLY

A-80

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 53 - H SOLENOID (ON-HIGHWAY), I SOLENOID (OFF-HIGHWAY)
3. If the chassis wiring harness is okay, check the internal components and circuits.
a. For on-highway transmissions, check resistance between bulkhead terminals K and N. Resistance should
be between 9 and 20 ohms.
b. For off-highway transmissions, check resistance between low-low valve body bulkhead terminals D and
B. Resistance should be between 12 and 24 ohms.
c. If resistance readings are incorrect, determine whether the problem is in the internal wiring harness
or the solenoid.
1) Remove the electrical connector from solenoid H (on-highway) or from solenoid I (off-highway).
2) Use an ohmmeter to check the solenoids internal resistance.
3) If solenoid resistance is incorrect, replace the solenoid.
4) If solenoid resistance is okay (9-20 ohms for on-highway, 12-24 ohms for off-highway), check the
solenoid circuits internal wiring harness wires for opens, shorts to each other, shorts to other wires
and shorts to ground. Isolate and repair problems as needed.
4. If the solenoids circuit resistance is okay, check related solenoid circuits for problems.
a. Refer to Troubleshooting Steps for Code 52. Isolate and repair problems as needed.
5. If the solenoids circuit resistance is okay, and related solenoid circuits are okay, replace the ECU. If
replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it, road testing the vehicle,
and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-81

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 54 - LATCHING SOLENOID CHAIN

ON HIGHWAY
J1B

J1

3M

11

SOL A OMITTED 4 SPEED

* SOL
A & B OMITTED 3 SPEED

TRANS
111

GRN

3L

14

114

WHT

1S

10

110

WHT

2T

20

120

BLU

1W

105

VIO

1T
3T

15
21

115
121

GRN NOT USED 3&4 SPEED

RED

NOT USED 3 SPEED

U
T
C

+
J

9-20

9-20

9-20

9-20

+
+

* 9-20
A* 9-20
B

CHECK FOR:
RESISTANCE TOO HIGH 3M-3T
ANY WIRE SHORTED TO GROUND

OFF HIGHWAY
J1B
3M
3L

115
116

GRN
YEL

A
B
M

1S

109

BLU

N
E
P

2T
1W

117
114

BLK
WHT

3T

108

YEL

D
C
L
K

CHECK FOR:
RESISTANCE TOO HIGH 3M-3T
ANY WIRE SHORTED TO GROUND

A-82

SOL A OMITTED IN
* LOCK
TO NEUTRAL

MAIN

COPYRIGHT 1994 GENERAL MOTORS CORP.

+
-A

VALVE BODY
12-24

+D

12-24

+
-C

12-24

+B

12-24

+
-E

12-24

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 54 - LATCHING SOLENOID CHAIN
This code means that the ECU has received improper signals from the solenoid chain. The solenoids in the onhighway solenoid chain are all latching. The solenoids in the off-highway solenoid chain are non-latching.
Some potential causes include:
Opens or shorts in on-highway chassis harness wires 111, 114, 110, 120, 105 (if used), 115 (if used),
and 121.
Opens or shorts in off-highway chassis harness wires 115, 116 (if used), 109, 117, 114, and 108.
Opens or shorts in on-highway electro-hydraulic valve body circuit between terminals D and C.
Opens or short in off-highway electro-hydraulic valve body circuit between terminals A and K.
Faulty solenoid(s).
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the solenoid chains resistance.
a. Remove the J1B connector from the ECU.
b. For on-highway transmissions, connect ohmmeter leads to J1B terminals 3M and 3T. Latching solenoid
chain resistance should be between 36 and 80 ohms (three speed models), 45 and 100 ohms (four speed
models) or 54 and 120 ohms (five speed models).
c. For off-highway transmissions, connect ohmmeter leads to J1B terminals 3M and 3T. Solenoid chain
resistance should be between 48 and 96 ohms (lock-in-range models) or 60 and 120 ohms (lock-inneutral models).
If readings are correct, proceed to Troubleshooting Step 4.
2. If resistance readings are incorrect, check the chassis wiring harness.
a. Remove the J1B connector from the ECU, and remove the bulkhead connector from the transmission.
b. For on-highway transmissions, check wires 111, 114, 110, 120, 105 (if used), 115 (if used) and 121 for
opens, shorts to each other, shorts to other wires and shorts to ground.
c. For off-highway transmissions, check wires 115, 116 (if used), 109, 117, 114 and 108 for opens, shorts to
each other, shorts to other wires and shorts to ground.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-83

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 54 - LATCHING SOLENOID CHAIN

ON-HIGHWAY

OFF-HIGHWAY
A

MAIN VALVE BODY

CONNECTOR

B
C

D
E
F

A-84

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 54 - LATCHING SOLENOID CHAIN
3. If the chassis wiring harness is okay, check the internal components and circuits.
a. For on-highway transmissions, check resistance between bulkhead terminals D and C. Resistance should
be between 36 and 80 ohms (three speed models), 45 and 100 ohms (four speed models) or 54 and 120
ohms (five speed models).
b. For off-highway transmissions, check resistance between bulkhead terminals A and K. Resistance should
be between 48 and 96 ohms (lock-in-range models) or 60 and 120 ohms (lock-in-neutral models).
c. If resistance readings are incorrect, determine whether the problem is in the internal wiring harness
or the solenoids.
1) Check each solenoid and related internal wiring circuit by following Troubleshooting Steps for Codes
41, 42, 43, 44, 45 and 46. Isolate and repair problems as needed.
4. If the solenoid chains resistance is okay, check individual solenoids and circuits for problems.
a. Refer to Troubleshooting Steps for Codes 41, 42, 43, 44, 45 and 46. Isolate and repair
problems as needed.
5. If the solenoid chains resistance is okay, and individual solenoid circuits are okay, replace the ECU. If
replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it, road testing the vehicle,
and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-85

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODES 61 AND 63 - G SOLENOID (OFF-HIGHWAY ONLY)

OFF HIGHWAY
J1A
LOCATION-VALVE BODY

ECU
G
H

I
N
T
E
R
N
A
L

110
118

WHITE
BLUE

2X
1X

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
G SOL 12-24

A-86

COPYRIGHT 1994 GENERAL MOTORS CORP.

J1B

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODES 61 AND 63 - G SOLENOID (OFF-HIGHWAY ONLY)
This code means that the ECU has received improper signals from the G solenoid circuit. Solenoid G controls the
flow of main pressure under the splitter shift valve during lock-in-range electrical failure.
Some potential causes include:
Opens or shorts in chassis harness wires 110 and 118.
Opens or shorts in electro-hydraulic valve body circuit between terminals G and H.
Faulty solenoid.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the solenoid circuits resistance.
a. Remove the J1B connector from the ECU.
b. Connect ohmmeter leads to J1B terminals 2X and 1X. Solenoid circuit resistance should be between 12
and 24 ohms.
If readings are correct, proceed to Troubleshooting Step 4.
2. If resistance readings are incorrect, check the chassis wiring harness.
a. Remove the J1B connector from the ECU, and remove the bulkhead connector from the transmission.
b. Check wires 110 and 118 for opens, shorts to each other, shorts to other wires and shorts to ground.
Isolate and repair problems as needed.
3. If the chassis wiring harness is okay, check the internal components and circuits.
a. Check resistance between bulkhead terminals G and H. Resistance should be between 12 and 24 ohms.
b. If resistance readings are incorrect, determine whether the problem is in the internal wiring harness
or the solenoid.
1) Remove the electrical connector from solenoid G.
2) Use an ohmmeter to check the solenoids internal resistance.
3) If solenoid resistance is incorrect, replace the solenoid.
4) If solenoid resistance is okay (12-24 ohms), check the solenoid circuits internal wiring harness wires
for opens, shorts to each other, shorts to other wires and shorts to ground. Isolate and repair problems
as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-87

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODES 61 AND 63 - G SOLENOID (OFF-HIGHWAY ONLY)

MAIN VALVE BODY

CONNECTOR

B
C

D
E
F

A-88

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODES 61 AND 63 - G SOLENOID (OFF-HIGHWAY ONLY)
4. If the solenoids circuit resistance, chassis wiring harness and internal wiring harness and components are
okay, replace the ECU. If replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it,
road testing the vehicle, and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-89

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 62 - F SOLENOID (OFF-HIGHWAY ONLY)

J1A
LOCATION-VALVE BODY

ECU
J
F

I
N
T
E
R
N
A
L

111
119

GREEN
RED

3X
3W

C
O
N
N
E
C
T
O
R

W
I
R
I
N
G
F SOL 12-24

A-90

COPYRIGHT 1994 GENERAL MOTORS CORP.

J1B

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 62 - F SOLENOID (OFF-HIGHWAY ONLY)
This code means that the ECU has received improper signals from the F solenoid circuit. Solenoid F controls the
splitter shift valve.
Some potential causes include:
Opens or shorts in chassis harness wires 111 and 119.
Opens or shorts in electro-hydraulic valve body circuit between terminals J and F.
Faulty solenoid.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the solenoid circuits resistance.
a. Remove the J1B connector from the ECU.
b. Connect ohmmeter leads to J1B terminals 3X and 3W. Solenoid circuit resistance should be between
12 and 24 ohms.
If readings are correct, proceed to Troubleshooting Step 4.
2. If resistance readings are incorrect, check the chassis wiring harness.
a. Remove the J1B connector from the ECU, and remove the bulkhead connector from the transmission.
b. Check wires 111 and 119 for opens, shorts to each other, shorts to other wires and shorts to ground.
Isolate and repair problems as needed.
3. If the chassis wiring harness is okay, check the internal components and circuits.
a. Check resistance between bulkhead terminals J and F. Resistance should be between 12 and 24 ohms.
b. If resistance readings are incorrect, determine whether the problem is in the internal wiring harness
or the solenoid.
1) Remove the electrical connector from solenoid F.
2) Use an ohmmeter to check the solenoids internal resistance.
3) If solenoid resistance is incorrect, replace the solenoid.
4) If solenoid resistance is okay (12-24 ohms), check the solenoid circuits internal wiring harness wires
for opens, shorts to each other, shorts to other wires and shorts to ground. Isolate and repair problems
as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-91

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 62 - F SOLENOID (OFF-HIGHWAY ONLY)

MAIN VALVE BODY

CONNECTOR

B
C

D
E
F

A-92

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 62 - F SOLENOID (OFF-HIGHWAY ONLY)
4. If the solenoids circuit resistance, chassis wiring harness and internal wiring harness and components are
okay, replace the ECU. If replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it,
road testing the vehicle, and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-93

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 66 - TRANSMISSION ENGINE COMMUNICATION LINK (TECL)
1C

238

238

3B
ECU 1D

240

240

239

239

3C

241

241

ECU

TTCL
(Transmission to Transmission
Communication Link)

1C

238

532

3B

240

533

ECU 1D

239

534

3C

241

535

242

461
243

L
M
F
DDL

A-94

DDEC I
ENGINE
CONTROL

451
244

510

TECL
(Transmission to Engine
Communication Link)

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 66 - TRANSMISSION ENGINE COMMUNICATION LINK (TECL)
This code means that the ECU senses a circuit problem with the Bi-Directional Communication Link (BDCL) or
Transmission/Engine Communication Link (TECL). BDCL lets two ECUs communicate, and TECL lets the
Electronic Controls ECU communicate with DDEC. Before troubleshooting the Electronic Control, verify proper
DDEC computer operation (if applicable).
Some potential causes include:
Improper DDEC computer operation.
Improper interface connections, opens or shorts in cab harness wires 238, 239, 240, 241, 242,
243 and 244.
Improper interface connections at TECL/DDEC wires 532, 533, 534, 535, 461, 451 and 510.
Wrong PROM for the application.
Faulty ECU.
NOTE:

This code is sometimes logged when a Diagnostic Data Reader (DDR) is plugged into the
Diagnostic Data Link (DDL). In this instance, no BDCL or TECL problems exist, but the code
should be manually cleared using the diagnostic switch.

TROUBLESHOOTING STEPS
1. Remove the cab harness connector (J1A) from the ECU.
a. If BDCL, remove cab harness connectors from both ECUs.
b. If TECL, remove the DDEC computer connector that contains the TECL interface wires.
2. Check the cab harness.
a. For BDCL, check cab harness wires 238, 239, 240 and 241 for opens, shorts to each other, shorts to other
wires and shorts to ground.
1) Make sure wires 238 and 240 are in a twisted pair.
2) Make sure wires 239 and 241 are in a twisted pair.
b. For TECL, check cab harness wires 238, 239, 240, 241, 242, 243 and 244 for opens, shorts to each other,
shorts to other wires and shorts to ground.
1) Make sure wires 238 and 240 are in a twisted pair.
2) Make sure wires 239 and 241 are in a twisted pair.
3) Check for proper interface connections between the TECL wires and DDEC wires 532, 533, 534,
535, 461, 451 and 510.
a) If necessary, check wires 532, 533, 534, 535, 461, 451 and 510 for opens, shorts to each other,
shorts to other wires and shorts to ground.
Isolate and repair problems as needed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-95

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 66 - TRANSMISSION ENGINE COMMUNICATION LINK (TECL)

THE INTERFACE MODULE

(SHOWN IN PHANTOM)
IS OEM-SUPPLIED AND
INCLUDES CONNECTORS

WIRE 124
WIRE 104
WIRE 106A

A
DDEC II
HARNESS

WIRE 908

THROTTLE INTERFACE
MODULE

C
"THROTTLE POSITION" SECTION
OF ELECTRONIC CONTROLS I
CHASSIS WIRING HARNESS

PACKARD CONNECTOR TO BE OEM-SUPPLIED

1-CAVITY
SEALS (1)
TERMINALS (1)

12015791
12015323
12034051

PACKARD CONNECTOR INCLUDED

ON ELECTRONIC CONTROLS HARNESS

PACKARD CONNECTOR ON MODULE

12010996
12015323
12033674

1-CAVITY CONNECTOR
SEALS (1)
TERMINALS (1)

12015793
12015323
12033674

3-CAVITY
SEALS (3)
TERMINALS (3)

PACKARD CONNECTOR ON MODULE

12010717
12015323
12034051

3-CAVITY
SEALS (3)
TERMINALS (3)

PACKARD CONNECTOR ON HARNESS

6-CAVITY CONNECTOR
SEALS (6)
TERMINALS (6)
CAVITY PLUG (1)
WIRE 438
GROUND
WIRE 606 OR
WIRE 972

WIRE 568
WIRE 903

2120647.37
12/9/92

PACKARD CONNECTOR ON MODULE

12015790
12015323
12034051
12010300

1-CAVITY CONNECTOR
SEALS (2)
TERMINALS (2)

12010972
12015323
12034051
WIRE 222

PACKARD CONNECTOR ON MODULE

A
B
C
D
E
F

12010975
12015323
12033674
12010300

6-CAVITY
SEALS (6)
TERMINALS (6)
CAVITY PLUG (1)

DDEC II
HARNESS

A
B

2-CAVITY CONNECTOR
SEALS (3)
TERMINALS (3)

ITEMS SHOWN IN PHANTOM

ARE CUSTOMER FURNISHED

A
B
C

WIRE 124
WIRE 104
WIRE 106A

PACKARD CONNECTOR ON MODULE

1-CAVITY CONNECTOR
SEAL (1)
TERMINAL (1)

12010996
12015323
12033874

PACKARD CONNECTOR ON HARNESS

PACKARD CONNECTOR ON HARNESS

12015791
12015323
12034061

PACKARD CONNECTOR ON MODULE

3-CAVITY CONNECTOR
SEALS (3)
TERMINALS (3)

12010973
12015323
12033674

THROTTLE POSITION
SECTION OF ATEC - 1
CHASSIS WIRING HARNESS

WIRE 908

1-CAVITY CONNECTOR
SEAL (1)
TERMINAL (1)

ATEC - 1 CAB
WIRING HARNESS

PACKARD CONNECTOR ON HARNESS

MAXIMUM FEATURE
THROTTLE INTERFACE
MODULE

CAVITY PLUG

WIRE 205

3-CAVITY CONNECTOR
SEALS (3)
TERMINALS (3)

12015793
12015323
12033674

12010717
12015323
12034051

2120647.38
12/9/92

A-96

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX A TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT
TROUBLE CODE 66 - TRANSMISSION ENGINE COMMUNICATION LINK (TECL)
3. If the cab wiring harness, interface connections and DDEC harness (if applicable) are okay, replace the ECU.
If replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it, road testing the
vehicle, and checking for codes.

___________________________________________________________________________________
TROUBLE CODE 69 - ECU
This code means that the ECU self-diagnostic system has detected a problem with the ECU itself. If an abnormal
condition is sensed by the ECU, the computer turns itself off. The Check Transmission and Do Not Shift lights
come on and all shifts are blocked.
A potential cause includes:
Improper vehicle interface connections.
Improper ECU mounting.
Faulty ECU.

TROUBLESHOOTING STEPS
1. Check the ECU for proper mounting.
a. Connectors should be clean, secure and undamaged.
b. The ECU should be mounted in a well-ventilated area protected from direct exposure to weather,
cleaning sprays, high concentrations of dust and sunlight.
c. The ECU should not be exposed to water (road splash, etc.).
d. The ECU should be mounted with its connectors down to avoid direct moisture contact
on the connectors.
Make corrections to ECU mounting provisions as needed before replacing the ECU.
2. Replace the ECU. If replacing the ECU fixes the problem, verify the old ECU is bad by reinstalling it, road
testing the vehicle, and checking for codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

A-97

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
The following pages include detailed troubleshooting information used when trouble codes are not present.
A thorough understanding of electronic control components and operation is necessary for
successful troubleshooting.
NOTE:

Refer to sections 1 through 7 in this manual for important, detailed operational and preliminary
troubleshooting information.

Troubleshooting steps are divided into three general categories:

Electronic Complaints
Hydraulic Complaints
Output Retarder Complaints
Use these steps plus the appropriate Service Manual and Parts Catalog to diagnose and repair problems that do
not create trouble codes.

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-1

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
CUSTOMER COMPLAINT INDEX
Electronic Complaints
Chart

Page

1. No CHECK TRANS Light At Ignition....................................................................................................... B-3

2. DO NOT SHIFT Light Will Not Go Out At Startup .................................................................................. B-4
3. CHECK TRANS Light Only - Will Not Go Out At Startup....................................................................... B-5
4. CHECK TRANS Light Goes Out Only When Drive Is Selected At Startup ............................................. B-6
5. Transmission Will Not Shift To Forward Or Reverse................................................................................. B-7
6. Vehicle Will Not Start (Will Not Crank)..................................................................................................... B-8
7. Transmission Does Not Shift Properly (Rough Shifts, Late Shifts, Early Shifts, Etc.) .............................. B-9
8. Transmission Will Not Make A Specific Shift ........................................................................................... B-10
9. CHECK TRANS Light Flashes But No Code Present ............................................................................... B-11
10. Transmission Will Not Stay In Forward Or Reverse .................................................................................. B-12

Hydraulic Complaints
1. Abnormal Automatic Shifts (Rough Shifts, Late Shifts, Early Shifts, Etc.)............................................... B-13
2. Abnormal Activities Or Responses............................................................................................................. B-14
3. Abnormal Stall Speeds................................................................................................................................ B-15
4. Leaking Oil (Output Shaft) ......................................................................................................................... B-16
5. Low Pressures ............................................................................................................................................. B-17
6. Slippage (General) ...................................................................................................................................... B-18
7. Excessive Flair (Engine Overspeed On Full Throttle Shifts) ..................................................................... B-19
8. Overheating In All Ranges.......................................................................................................................... B-20
9. Transmission Throws Oil Out Of Fill Tube/Breather ................................................................................. B-21
10. Dirty Oil ...................................................................................................................................................... B-22
11. Noise Occurring Intermittently (Buzzing) .................................................................................................. B-23
12. Vehicle Will Not Push Start ........................................................................................................................ B-24

Retarder Complaints
1. Excessive Retarder Response Time ............................................................................................................ B-25
2. Poor Or No Retarder Performance.............................................................................................................. B-26
3. Oil Spewing ................................................................................................................................................ B-27
4. Transmission Oil Light Illuminated ............................................................................................................ B-28
5. Excessive Retarder Capacity....................................................................................................................... B-29
6. Retarder Not Releasing ............................................................................................................................... B-30
7. Harsh Retarder Apply ................................................................................................................................. B-31

B-2

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
ELECTRONIC COMPLAINT - CHART 1
PROBLEM
No CHECK TRANS Light At
Ignition

PROBABLE CAUSE

SUGGESTED REMEDY

Faulty light bulb

Replace light bulb

Faulty relay

Replace relay

Incorrect power to relay

Check power line from ignition

switch to relay and repair

Faulty cab wiring harness

Check wiring between ECU and

CHECK TRANS light, and repair
where necessary

Faulty ECU

Replace ECU

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-3

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
ELECTRONIC COMPLAINT - CHART 2
PROBLEM

PROBABLE CAUSE

SUGGESTED REMEDY

DO NOT SHIFT Light Will Not

Go Out At Startup
A.

B.

B-4

Vehicle Drives Normally

Vehicle Does Not Drive

Percent throttle is too high

Adjust throttle position sensor. If

necessary, troubleshoot Code 21

Faulty shift selector

Troubleshoot Codes 23, 31

Faulty ECU

Replace ECU

Faulty power relay

Replace relay

Faulty cab harness

Repair cab harness

Faulty wiring

Repair wiring

Oil temperature too low

Troubleshoot Codes 24 and 33

Faulty ECU

Replace ECU

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
ELECTRONIC COMPLAINT - CHART 3
PROBLEM

PROBABLE CAUSE

SUGGESTED REMEDY

CHECK TRANS Light Only Will Not Go Out At Startup

(DO NOT SHIFT Light Is Out)
A.

B.

Vehicle Drives Normally

Vehicle Does Not Drive

Faulty CHECK TRANS relay

Replace relay

Faulty cab harness

Repair harness

Incorrect wiring to CHECK

TRANS light

Repair wiring

Faulty ECU

Replace ECU

Faulty engine pressure switch

Replace engine oil pressure switch

Engine oil pressure low

Diagnose and repair cause

of problem

Oil temperature too low

Troubleshoot Codes 24 and 33

Faulty ECU

Replace ECU

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-5

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
ELECTRONIC COMPLAINT - CHART 4
PROBLEM
CHECK TRANS Light Goes Out
Only When Drive Is Selected
At Startup

B-6

PROBABLE CAUSE
Percent throttle is incorrect

COPYRIGHT 1994 GENERAL MOTORS CORP.

SUGGESTED REMEDY
Check throttle position sensor
adjustment. If necessary,
troubleshoot Code 21

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
ELECTRONIC COMPLAINT - CHART 5
PROBLEM
Transmission Will Not Shift
To Forward Or Reverse
(Stays In Neutral)

PROBABLE CAUSE

SUGGESTED REMEDY

Extremely low oil level

Add oil to proper level

Oil temperature too low

Troubleshoot Codes 24 and 33

Voltage too low to ECU

Troubleshoot Code 13

Faulty throttle position sensor

Troubleshoot Code 21

Faulty shift selector

Troubleshoot Code 23

Faulty bulkhead connector

terminal connections

Check bulkhead connector for

proper continuity between external
and internal terminals

Faulty wiring harnesses

Repair harnesses

Faulty speed sensor

Troubleshoot Code 22

Faulty H solenoid circuitry

Troubleshoot Codes 41 through 46

Faulty F, D or J solenoid circuitry

Troubleshoot Codes 41 through 46

Hydraulic problems

Refer to Hydraulic Complaint,

Chart 2

Faulty ECU

Replace ECU

Special input wire 222 open and

neutral range inhibit in PROM

Ground wire 222

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-7

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
ELECTRONIC COMPLAINT - CHART 6
PROBLEM
Vehicle Will Not Start
(Will Not Crank)

B-8

PROBABLE CAUSE

SUGGESTED REMEDY

Dead battery

Recharge battery

Voltage to shift selector too low

Troubleshoot Code 23

Faulty starter circuit

Repair vehicle starter circuit

Faulty neutral start relay

Replace neutral start relay

Faulty wiring in neutral

start circuit

Repair wiring

Faulty engine oil pressure switch

Check/replace engine oil

pressure switch

Faulty shift selector

Troubleshoot Code 23

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
ELECTRONIC COMPLAINT - CHART 7
PROBLEM
Transmission Does Not Shift
Properly (Rough Shifts, Late
Shifts, Early Shifts, Etc.)

PROBABLE CAUSE

SUGGESTED REMEDY

Faulty throttle position

sensor circuitry

Troubleshoot Code 21

Faulty speed sensor circuitry

Troubleshoot Code 22

Incorrect PROM

Check PROM part number and

replace. Troubleshoot Code 34

Faulty trim boost E

solenoid circuitry

Troubleshoot Code 52

Intermittent problems

Check bulkhead connector

and related circuitry for
proper continuity

Crossed wires in harness

Check and repair chassis

harness as needed

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-9

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
ELECTRONIC COMPLAINT - CHART 8
PROBLEM
Transmission Will Not Make A
Specific Shift

B-10

PROBABLE CAUSE

SUGGESTED REMEDY

Extremely low oil level

Add oil to proper level

Extreme oil temperature

Troubleshoot Codes 24 and 33

Faulty C solenoid circuitry

Troubleshoot Codes 41 through 46

Faulty speed sensor circuitry

Troubleshoot Code 22

Faulty shift selector circuitry

Troubleshoot Code 23

Hydraulic problem

Refer to Hydraulic Complaint Chart 2

Faulty ECU

Replace ECU

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
ELECTRONIC COMPLAINT - CHART 9
PROBLEM
CHECK TRANS Light Flashes
But No Code Present

PROBABLE CAUSE

SUGGESTED REMEDY

Intermittent power to ECU

Check input power to ECU and

correct if necessary

Loose CHECK TRANS relay

Replace CHECK TRANS relay

Loose wiring to CHECK

TRANS light

Repair wiring

Faulty or incorrect ground

wire attachment

Repair ground circuit

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-11

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
ELECTRONIC COMPLAINT - CHART 10
PROBLEM
Transmission Will Not Stay In
Forward Or Reverse (This May Be
Normal System Response To Code
14 or 15)

B-12

PROBABLE CAUSE

SUGGESTED REMEDY

Pressure switch faulty

Replace pressure switch

Leaking at solenoid assembly

Rebuild solenoid assembly

Faulty solenoid - leaking

Replace solenoid

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
HYDRAULIC COMPLAINT - CHART 1
PROBLEM
Abnormal Automatic Shifts
(Rough Shifting, Late Shifts,
Early Shifts)

PROBABLE CAUSE

SUGGESTED REMEDY

Control valve sticking

Overhaul valve body assembly

Trimmer valves sticking

Overhaul valve body assembly

Trim boost regulator sticking

Overhaul valve body assembly

Engine idle speed too fast (N to D)

Adjust engine idle (refer to vehicle

service manual)

Electronic problems

Refer to Electronic Complaint Chart 7

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-13

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
HYDRAULIC COMPLAINT - CHART 2
PROBLEM

PROBABLE CAUSE

SUGGESTED REMEDY

Abnormal Activities Or Responses

A.

Excessive Creep In First

And Reverse Ranges

Engine idle speed too high

Adjust to correct idle speed (refer

to vehicle service manual)

B.

No Response To
Shift Selector

Main pressure low

Refer to Hydraulic Complaint Chart 5

Low oil level

Fill to proper level

Valves sticking

Overhaul valve body assembly

Electronic problem

Refer to Electronic Complaint Chart 5

C.

Vehicle Moves Forward

In Neutral

Forward clutch failed, dragging, or

not released

Rebuild forward clutch (refer to

transmission service manual)

D.

Vehicle Moves Backward

In Neutral

Fourth clutch failed, dragging, or

not released

Rebuild fourth clutch (refer to

transmission service manual)

B-14

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
HYDRAULIC COMPLAINT - CHART 3
PROBLEM

PROBABLE CAUSE

SUGGESTED REMEDY

Abnormal Stall Speeds

A.

B.

High Stall Speeds

Low Stall Speeds

Low oil level

Add oil to proper level

Clutch pressure low

Refer to Hydraulic Complaint Chart 5

Forward clutch slipping (forward)

Rebuild forward clutch (refer to

transmission service manual)

First clutch slipping

Rebuild first clutch

Fourth clutch slipping (reverse)

Rebuild fourth clutch

Engine not performing efficiently

(plugged injectors, high altitude,
dirty filters, etc.)

Refer to engine or vehicle service

manual

Lockup clutch partially applied

Rebuild lockup clutch

Torque converter

Replace or rebuild converter

Stall speeds of 66% of normal

implies freewheeling stator

Replace or rebuild converter

Incorrect converter

Replace converter

Transmission too hot

Inspect cooling system

components and check oil level

Higher power engine

Confirm proper engine match

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-15

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
HYDRAULIC COMPLAINT - CHART 4
PROBLEM
Leaking Oil (Output Shaft)

B-16

PROBABLE CAUSE

SUGGESTED REMEDY

Faulty or missing seal at

output flange

Install new lip-type seal in rear of

transmission housing (refer to
appropriate service manual)

Flange worn at seal surface

Replace flange

Insufficient sealant around

seal O.D.

When replacing seal, apply

sufficient sealant

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
HYDRAULIC COMPLAINT - CHART 5
PROBLEM

PROBABLE CAUSE

SUGGESTED REMEDY

Low Pressures
A.

B.

C.

Low oil level

Add oil to proper level

Oil filter element clogged or faulty

Replace oil filter

Sealring on oil suction tube

leaking or missing

Install new oil filter pickup tube

sealring and lubricate the sealring
with the same oil as used to refill
the transmission

Valves sticking (trimmers, relays,

and main pressure regulator)

Overhaul valve body assembly

Main pressure regulator valve

spring weak

Check spring and replace

if necessary

Control valve body leakage

Replace or rebuild control

valve body assembly. Take care
when removing and labeling
shift springs

Oil pump worn or damaged

Replace or rebuild oil pump

Missing priority valve

Replace missing valve

Incorrect main valve

Replace incorrect valve

Low Main Pressure In

First Gear, Normal
Pressure In Other
Forward Ranges

First range circuit of control valve

body leaking

Replace or rebuild control

valve body

Excessive leakage at first clutch

piston seals

Overhaul transmission;
replace seals

Low Lubrication Pressure

Low oil level

Refer to Item A, first Suggested

Remedy

Engine idle speed too low

Refer to vehicle service manual

Excessive internal oil leakage

Check other pressures (above

items); also check valve body
mounting bolts; lubrication valve
seat and spring

Cooler lines restricted or leaking

Check for kinks, leakage; reroute

or replace lines as necessary

Lubrication valve spring weak

Refer to Item A, sixth Suggested

Remedy

Lubrication valve not seating

Replace lubrication valve

Low Main Pressure In

All Ranges

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-17

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
HYDRAULIC COMPLAINT - CHART 6
PROBLEM

PROBABLE CAUSE

SUGGESTED REMEDY

Slippage (General)
A.

B.

B-18

Excessive Slippage And

Clutch Chatter In Only
One Range

Slippage In All
Forward Ranges

Clutch slipping in that range

Overhaul the slipping clutch

Excessive oil leakage in range

piston seals

Overhaul clutch and piston

assembly

Oil leakage in valve components

for that particular range

Overhaul control valve body

assembly

Trimmer stuck open

Check trimmer valve for free

movement or broken sealring.
Overhaul trimmer valve

Cycling priority valves

Inspect priority valves

Hydraulically failed solenoid

Overhaul solenoid assembly

Low oil level

Add oil to proper level

Clutch main pressure low

See Low Pressures (Chart 5)

Forward clutch slipping

Rebuild forward clutch (refer to

transmission service manual)

Sealrings on front bearing

retainer broken

Replace sealrings

Hydraulically failed solenoid

Overhaul solenoid assembly

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
HYDRAULIC COMPLAINT - CHART 7
PROBLEM
Excessive Flair -Engine
Overspeed On Full
Throttle Upshifts

PROBABLE CAUSE

SUGGESTED REMEDY

Throttle sensor misadjusted

Adjust sensor; if necessary

troubleshoot Code 21

Sticking trimmers

Check trimmer valves and confirm

correct springs

Wrong trimmer springs

Refer to Item 2

Malfunctioning trim boost circuit

Check trim boost circuitry

Piston seals leaking or clutch

plates slipping in range involved

Overhaul transmission (see

applicable transmission service
manual)

Broken sealrings

Replace sealrings

Forward clutch piston seals or

clutch plates slipping (all upshifts)

Overhaul forward clutch and

piston assembly

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-19

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
HYDRAULIC COMPLAINT - CHART 8
PROBLEM
Overheating In All Ranges

B-20

PROBABLE CAUSE

SUGGESTED REMEDY

Aerated oil - oil too high or low

Adjust oil to proper level; check

for defective sealring at suction
tube; check for defective pump

Oil cooler lines restricted/bypass

valve stuck open

Remove restrictions, clean or

replace lines (refer to vehicle
service manual)

Torque converter

Replace or repair
converter assembly

Cooler flow loss due to

internal leakage

Overhaul transmission

Engine overheat

Correct overheat situation (refer to

vehicle service manual)

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
HYDRAULIC COMPLAINT - CHART 9
PROBLEM
Transmission Throws Oil Out Of
Fill Tube And/Or Breather

PROBABLE CAUSE

SUGGESTED REMEDY

Dipstick loose

Tighten cap. Replace if necessary

Oil level too high

Drain to proper level

Oil level too low

Add oil to proper level

Fill tube not vented/plugged

Check for blockage and clean

where necessary

Breather stopped up (clogged)

Clean or replace breather

Water in oil

Drain and replace oil

Dipstick gasket worn

Replace gasket or dipstick

Improper dipstick marking (high

oil level)

Replace dipstick

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-21

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
HYDRAULIC COMPLAINT - CHART 10
PROBLEM
Dirty Oil

B-22

PROBABLE CAUSE

SUGGESTED REMEDY

Failure to change oil at

proper intervals

Change oil and install new filter

Excessive heat

Refer to Overheating
(Chart 8, Item 4)

Clutch failure

Overhaul transmission

Damaged oil filter

Replace oil filter

Engine rear oil seal failed

Replace oil seal

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
HYDRAULIC COMPLAINT - CHART 11
PROBLEM
Noise Occurring Intermittently
(Buzzing)

PROBABLE CAUSE

SUGGESTED REMEDY

Low oil level

Add oil to proper level

Air leak at oil suction tube

(O-ring broken)

Replace oil suction tube seal and

filter (refer to transmission
service manual)

Clogged filter

Replace filter

Aerated oil

Improper oil level; improper or

contaminated oil

Hole in filter

Replace filter

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-23

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
HYDRAULIC COMPLAINT - CHART 12
PROBLEM
Vehicle Will Not Push Start

B-24

PROBABLE CAUSE
Normal operation (no rear pushstart pump)

COPYRIGHT 1994 GENERAL MOTORS CORP.

SUGGESTED REMEDY

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
OUTPUT RETARDER COMPLAINT - CHART 1
PROBLEM
Excessive Retarder
Response Time

PROBABLE CAUSE

SUGGESTED REMEDY

Low air pressure in supply tank

Repair supply tank as needed

Faulty retarder apply air regulator

Repair or replace the regulator

as needed

Leaking or incorrectly sized

air lines

Repair leak or install correctly

sized lines

Retarder control valve sticking

Clean or replace valve if damaged.

Replace valve body if required

Pressure regulator valve sticking

Refer to Item 4

External check valve sticking

Clean or replace check

valve assembly

Charging valve sticking

Refer to Item 4

Priority valve sticking

Refer to Item 4

Clutch clearance excessive

Correct clutch clearance per

service manual

Clutch piston seals leaking

Replace leaking seals

Accumulator piston seals leaking

Replace leaking seals

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-25

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
OUTPUT RETARDER COMPLAINT - CHART 2
PROBLEM
Poor Or No Retarder Performance

B-26

PROBABLE CAUSE

SUGGESTED REMEDY

Vehicle retarder on-off switch off

Assure switch is working and on

No/low air pressure in supply tank

Repair as needed

Faulty retarder apply

pressure regulator

Repair or replace air lines

as needed

Leaking retarder apply air line

Repair or replace air lines

as needed

Faulty retarder/ throttle interlock

Adjust/repair/replace as needed

Leaking retarder control valve

assembly air seal

Replace faulty seal

Sticking retarder control valve

Clean or replace valve if damaged

Sticking pressure regulator valve

Refer to Item 6

Sticking charging valve

Refer to Item 6

Faulty transmission governor

Service per service manual

Incorrect clutch or charging

valve springs

See parts catalog

Sticking priority valve

Replace leaking seals

Leaking clutch piston seals

Replace leaking seals

Leaking accumulator seals

Replace leaking seals

Leaking rotor hub seals

Replace leaking seals

Low transmission main pressure

See Hydraulic Complaint - Chart 5

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
OUTPUT RETARDER COMPLAINT - CHART 3
PROBLEM
Oil Spewing

PROBABLE CAUSE

SUGGESTED REMEDY

Incorrect oil level

Obtain correct oil level per service

manual

Breather clogged

Clean or replace breather cap

assembly and ensure transmission
internal breather passage is open

Leaking retarder valve body

air seal

Replace leaking seals

Failed oil/water heat exchanger

(this condition may be indicated
by transmission fluid in the
cooling fluid)

Repair as needed

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-27

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
OUTPUT RETARDER COMPLAINT - CHART 4
PROBLEM
Transmission Oil
Light Illuminated

B-28

PROBABLE CAUSE

SUGGESTED REMEDY

Incorrect oil level

Obtain correct oil level per

service manual

Faulty temperature sensor

Troubleshoot Code 33

Faulty retarder air

pressure regulator

Repair or replace as needed

Sticking retarder control valve

Clean or replace valve. Replace

valve body if needed

Clogged heat exchanger

Disassemble and clean, recore,

or replace

Incorrect size oil/water

heat exchanger

Check OEM recommendation

Clutch clearance insufficient

Adjust clearance per service

manual instructions

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
OUTPUT RETARDER COMPLAINT - CHART 5
PROBLEM
Excessive Retarder Capacity

PROBABLE CAUSE

SUGGESTED REMEDY

Wrong pressure regulator

valve spring

See parts catalog

Pressure regulator valve plug

installed backward

Install clutch valve plug per

service manual

Pressure regulator valve

plug sticking

Clean or replace plug. Replace

valve body if needed

Pressure regulator valve sticking

Refer to Item 3

Clutch clearance insufficient

Establish clutch clearance per

service manual

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-29

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
OUTPUT RETARDER COMPLAINT - CHART 6
PROBLEM
Retarder Not Releasing

B-30

PROBABLE CAUSE

SUGGESTED REMEDY

Faulty retarder air

pressure regulator

Repair or replace regulator

as needed

Faulty retarder/throttle interlock

Adjust, repair or replace

interlock components

Sticking retarder control valve

Clean or replace valve. Replace

valve body if required

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES
OUTPUT RETARDER COMPLAINT - CHART 7
PROBLEM
Harsh Retarder Apply

PROBABLE CAUSE

SUGGESTED REMEDY

Pressure regulator plug valve

incorrectly installed or omitted

Install plug valve correctly

(dimple on valve must be
toward springs)

Pressure regulator valve stuck

Clean or replace valve. Replace

valve body if required

COPYRIGHT 1994 GENERAL MOTORS CORP.

B-31

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX B TROUBLESHOOTING STEPS - NO TROUBLE CODES

B-32

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
Contents

Page

Sealed ECU and Lever Shift Selector Connectors.............................................................................................. C-2

Bolt-Down Solenoid And Pressure Switch Connectors ..................................................................................... C-5
Diagnostic Data Link (DDL) Connectors ........................................................................................................... C-7
Throttle Position Sensor And On-Highway Speed Sensor Connectors .............................................................. C-9
Push Button Shift Selector Connectors............................................................................................................... C-13
Transmission Bulkhead And Digital Display Unit (DDU) Connectors.............................................................. C-15
Transmission Engine Communication Link (TECL) Connectors ...................................................................... C-17
Off-Highway Speed Sensor And Soldered Cannon Connectors......................................................................... C-19
Repairing A Broken Wire ................................................................................................................................... C-22
Repairing A Twisted Shielded Wire ................................................................................................................... C-24

COPYRIGHT 1994 GENERAL MOTORS CORP.

C-1

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
SEALED ECU AND LEVER SHIFT SELECTOR CONNECTORS

C-2

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
SEALED ECU AND LEVER SHIFT SELECTOR CONNECTORS
Part Numbers
J1A Cab Harness Connector

12034404

J1B Chassis Harness Connector

12034406

J3 Secondary Harness Connector

12034390

Lever Shift Selector Connector

12040921

Terminal

12047680

Sealing Plug

12034413

Special Tools
Remover Tool

J35689

Crimper Tool

J35123

NOTE:

These are pull to seat terminals. Do not solder crimps.

Procedures
A. Terminal Removal
1. Insert needle end of terminal remover J35689 into the small notch in the cavity of the terminal being
removed. Move the holding prong toward the terminal.
2. Push the wire and terminal out of the connector (this is a pull to seat terminal).
3. Pull the terminal as far as necessary from the connector. This will be limited by the number of other wires
inserted into the connector and by the distance between the back side of the connector and the beginning
of the harness covering.
4. Remove the terminal by cutting the wire as close to the terminal as possible. This minimizes the amount
of harness wire used during the repair.
B. Terminal Crimping
1. The wire should be pushed through the proper hole in the seal (green) and out the other side of the
connector prior to stripping.
2. Strip approximately 0.148 to 0.167 inch (3.76 to 4.24 mm) insulation from the wire.
3. Push open the terminal holder on crimper tool J35123 and insert a terminal into the opening marked
18-16. Position the terminal so that the crimp ends point up. Release the terminal holder.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
SEALED ECU AND LEVER SHIFT SELECTOR CONNECTORS (CONTD)
4. Slightly close the crimping tool until one click is heard. Do not start to crimp the terminal. Orient the
terminal so it is in the same position as it will be when pulled back into the connector.
5. Insert the wire into the terminal until the wire hits the holder. This positions the wire and insulation for
the crimp.
6. Squeeze the crimper fully until it opens when released.
7. Open the terminal holder and remove the wire and terminal from the crimping tool.
8. Pull on the terminal to assure the crimp is tight.
9. Position the terminal so that the holding prong aligns with the appropriate notch in the connector cavity.
10. Pull the wire and terminal completely into the cavity. A click should be heard and the terminal should
stay in place if the wire is pushed.
11. Plug unused openings in the wire seal with sealing plug part number 12034413.

C-4

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
BOLT-DOWN SOLENOID AND PRESSURE SWITCH CONNECTORS
Part Numbers
Latching Solenoid Connector

12059716

Non-Latching Solenoid Connector

12059718

Forward Pressure Switch Connector

12059717

Reverse Pressure Switch Connector

12059717

Lube Pressure Switch Connector

12059719

Terminal

12052410

Special Tools
Crimper Tool

J25563

Remover Tool

J33095

Procedures
A. Terminal Removal
1. Lift the secondary lock from the back end of the connector. Use a small screwdriver or pick in either slot
of the secondary lock.
NOTE:

Connector 12059717 does not allow access to the secondary lock slots. This connector cannot be
serviced and must be replaced.

2. Insert remover tool J33095 into the front (open) end of the connector.
3. Push the terminal holding prong straight and pull the wire and terminal out the back end of the connector.
B. Terminal Crimping
1. Remove the terminal by cutting the wire as close to the terminal as possible. This minimizes the amount
of harness wire used during the repair.
2. Strip approximately 0.226 to 0.246 inch (6.0 0.25 mm) of insulation from the wire.
3. Insert the terminal into crimping tool J25563.
4. The u shaped portion of the tool should hold the flat area of the terminal. The m shaped portion of
the tool should close around the open edge of the terminal. Use the small crimping area of the tool.
5. Insert wire so that the stripped portion is in the area to be crimped and the insulated portion is in the other
crimping area.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
BOLT-DOWN SOLENOID AND PRESSURE SWITCH CONNECTORS (CONTD)
6. Crimp the stripped section of wire.
7. Remove the terminal from the crimping tool.
8. Use a pair of needle nose pliers to start the bend on the terminal area that crimps around the insulation.
9. Crimp the insulated section of wire using the area behind the crimping tool pivot.
10. Remove the terminal from the crimping tool.
11. Tug on the terminal to assure the crimp is tight.
12. Insert the terminal into the connector with the holding prong toward the connector.
13. The terminal should click into place and not pull out.

C-6

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
DIAGNOSTIC DATA LINK (DDL) CONNECTOR
Part Numbers
DDL Connector

12020043

Terminal

12015823

Secondary Lock

12020219

Special Tools
Crimper Tool

J25563

Remover Tool

J33095

Procedures
A. Terminal Removal
1. Remove the secondary lock from the back end of the connector. Use a small screwdriver or pick in the
slots on each side of the connector.
2. Insert remover tool J33095 into the front (open) end of the connector at the terminal being repaired.
3. Push the terminal holding prong straight and pull the wire and terminal out the back end of the connector.
Cut the wire as close to the terminal as possible to minimize wire loss.
B. Terminal Crimping
1. Strip approximately 0.226 to 0.246 inch (6.0 0.25 mm) of insulation from the end of the wire.
2. Insert the terminal into the crimping tool.
3. The u shaped portion of the tool should hold the flat area of the terminal. The m shaped portion of
the tool should close around the open edge of the terminal. Use the small crimping area of the tool.
4. Slightly close the crimping tool to hold the terminal steady.
5. Insert the wire so that the stripped portion is in the area to be crimped and the insulated portion is in the
other crimping area.
6. Crimp the stripped section of wire.
7. Remove the terminal from the crimping tool.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
DIAGNOSTIC DATA LINK (DDL) CONNECTOR (CONTD)
8. Use a pair of needle nose pliers to start the crimp around the insulation.
9. Crimp the insulated section of wire using the area behind the crimping tool pivot.
10. Remove the terminal from the crimping tool.
11. Tug on the terminal to assure the crimp is tight.
12. Insert the terminal into the connector with the holding prong toward the center line of the connector.
13. The terminal should click into place and should not pull out.
14. Reinstall the secondary lock.

C-8

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
THROTTLE POSITION SENSOR AND ON-HIGHWAY SPEED SENSOR CONNECTORS
Part Numbers
Speed Sensor Connector

12015792

Throttle Sensor Connector

12015793

Speed Sensor Terminal

12034051

Throttle Sensor Terminal

12033674

Wire Seal

12015284

Special Tools
Crimping Tool

J25563

Remover Tool

J28742-A

Alternate Crimping Tool

J35606

Procedures
A. Terminal Removal
1. Unlatch and open the secondary lock on the connector.
2. Insert remover tool J28742-A in the front of the connector, over the terminal. Push the tool over the
terminal and pull the terminal out the back of the connector.
3. Cut the wire as close to the terminal as possible to minimize wire loss.
B. Terminal Crimping Using Crimping Tool J25563
1. Place the wire seal on the wire before stripping.
2. Strip approximately 0.226 to 0.246 inch (6.0 0.25 mm) of insulation from the wire.
3. Insert the terminal into the crimping tool.
4. The u shaped portion of the tool should hold the flat area of the terminal. The m shaped portion of
the tool should close around the open edge of the terminal. Use the small crimping area of the tool.
5. Slightly close the crimping tool to hold the terminal steady.
6. Insert wire so that the stripped portion is in the area to be crimped and the insulated portion is in the other
crimping area.
7. Crimp the stripped section of the wire.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
THROTTLE POSITION SENSOR AND ON-HIGHWAY SPEED SENSOR
CONNECTORS (CONTD)

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
THROTTLE POSITION SENSOR AND ON-HIGHWAY SPEED SENSOR CONNECTORS
8. Remove the terminal from the crimping tool.
9. Push the wire seal into the terminal. The second crimp will wrap around the wire seal. This will seal the
insulated area of the wire.
10. Use a pair of needle nose pliers to form the terminal prongs around the wire seal.
11. Tug on the terminal and be sure the crimp is tight.
12. Be sure the second crimp is tight around the wire seal.
13. Insert the terminal into the connector. The terminal should click into place and should not pull out.
14. Secure the secondary lock. Both sides of the connector must be latched.
C. Terminal Crimping Using Crimping Tool J35606
1. Place the wire seal on the wire before stripping.
2. Strip approximately 0.226 to 0.246 inch (6.0 0.25 mm) of insulation from the wire.
3. Insert the terminal into the crimping tool.
4. Position the terminal so the fingers are pointing up from the bottom jaw of the crimper.
5. Slightly close the crimping tool to hold the terminal steady.
6. Slide the wire seal to the edge of the insulation and insert the wire and seal into the terminal.
7. Position the wire and seal and squeeze the crimping tool until it opens when released.
8. Tug on the terminal to make sure the crimp is tight.
9. Make sure the crimp around the seal is tight.
10. Insert the terminal into the connector. The terminal should click into place and should not pull out.
11. Relatch the secondary lock. Both sides must latch.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
THROTTLE POSITION SENSOR AND ON-HIGHWAY SPEED SENSOR
CONNECTORS (CONTD)

C-12

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
PUSH BUTTON SHIFT SELECTOR CONNECTOR
Part Numbers
Shift Selector Connector

23016193

Terminal

23015204

Cable Clamp

23016490

Special Tools
Crimper Tool

J25563

Remover Tool

J34823

Procedures
A. Terminal Removal
1. Remove the cable clamp from the connector.
2. Insert removal tool J34823 into the top side of the connector, over the terminal being removed.
3. Push down on the plunger end of the tool.
4. Pull the terminal out the bottom of the connector. Cut the wire as close to the terminal as possible to
minimize wire loss.
B. Terminal Crimping
1. Strip approximately 0.148 to 0.167 inch (4.0 0.25 mm) of insulation from the end of the wire.
2. Insert the new terminal into crimping J25563.
3. The u shaped portion of the tool should hold the flat area of the terminal. The m shaped area should
close around the open edge of the terminal. Use the small crimping areas of the tool.
4. Slightly close the crimping tool to hold the terminal steady.
5. Insert the wire so that the stripped portion is in the area being crimped and the insulated portion is in the
other crimping area.
6. Crimp the stripped section of wire.
7. Remove the terminal from the crimping tool.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
PUSH BUTTON SHIFT SELECTOR CONNECTOR (CONTD)
8. Use a pair of needle nose pliers to start the bend on the terminal area of the insulation crimp.
9. Crimp the insulated section of wire.
10. Remove the terminal from the crimping tool and tug on the terminal to make sure the crimp is tight.
11. Insert the terminal into the connector. The terminal should click into place and should not pull out.
12. Install the cable clamp. Install the two phillips-head screws.

C-14

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
TRANSMISSION BULKHEAD AND DIGITAL DISPLAY UNIT (DDU) CONNECTORS
Part Numbers
Bulkhead Connector

23016498

DDU Connector

23048225

Terminal

23016502

Sealing Plug

23016504

Special Tools
Crimper Tool

J34182

Remover Tool

J34513

Procedures
A. Terminal Removal
1. Slide pin remover J34513, tapered end first, onto the damaged wire.
2. Work the pin remover tool into the connector socket until it locks onto the terminal. Pull the remover
tool, terminal and wire from the connector socket.
3. Repeat steps 1 and 2 for each damaged wire or terminal.
4. Cut the wire as close to the terminal as possible to minimize wire loss.
B. Terminal Crimping
1. Strip approximately 0.236 to 0.315 inch (6 to 8 mm) of insulation from the wire.
2. Set wire size indicator on crimping tool J34182 to wire size no. 18. Remove the indicator wire retainer.
Lift and rotate the indicator until the wire size is opposite the Sel. No. arrow. Replace the indicator
wire retainer.
3. Insert the terminal, long end first, into tool J34182. Close the crimping tool just enough to hold the
terminal. Back off the locking not so the adjusting screw is free. Turn the adjusting screw until the top of
the terminal is above the crimping hole. Tighten the locking nut against the crimping tool.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
TRANSMISSION BULKHEAD AND DIGITAL DISPLAY UNIT (DDU)
CONNECTORS (CONTD)
4. Insert the stripped end of the no. 18 wire into the terminal. Be sure the wire is fully inserted. Squeeze the
crimping tool handles together until the ratchet in the crimping tool releases. Remove the wire and
terminal from the crimping tool. Tug on the wire to make sure the crimp is tight.
5. Install the terminal into its proper socket in the connector. The terminal will click into position and
cannot be removed when properly installed.

C-16

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
TRANSMISSION ENGINE COMMUNICATION LINK (TECL) CONNECTOR
Part Numbers
TECL Connector

12047938

Terminal

12048074

Secondary Lock

12047936

Wire Seal

12048086

Special Tools
Remover Tool

J35689-A

Crimping Tool

J25563

Procedures
A. Terminal Removal
1. Unlatch and open the secondary lock on the connector.
2. Insert needle end of the remover tool into the small notch between the terminal and the connector. Pry the
holding prong against the terminal.
3. Pull on the attached wire and draw the terminal from the back of the connector.
4. Cut the wire as close to the terminal as possible to minimize wire loss.
B. Terminal Crimping
1. Place the wire seal on the wire before stripping.
2. Strip approximately 0.226 to 0.246 inch (6.0 0.25 mm) insulation from the wire.
3. Insert the terminal into the crimping tool.
4. The u shaped portion of the tool should hold the flat area of the terminal. The m shaped portion of
the tool should close around the open edge of the terminal. Use the small crimping area of the tool.
5. Slightly close the crimping tool to hold the terminal steady.
6. Insert the wire so that the stripped portion is in the area to be crimped and the insulated portion is in the
other crimping area.
7. Crimp the stripped section of wire.
8. Remove the terminal from the crimping tool.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
TRANSMISSION ENGINE COMMUNICATION LINK (TECL) CONNECTOR (CONTD)
9. Push the wire seal into the terminal. The second crimp will wrap around the wire seal. This will seal the
insulated area of wire.
10. Use a pair of needle nose pliers to crimp the insulated area.
11. Tug on the terminal to make sure the crimp is tight.
12. Align the holding prong with the small notch and insert the terminal into the connector. The terminal
should click into place and should not pull out.
13. If the terminal size prevents proper installation in the connector, crimp (squeeze) the terminal again 90
degrees from the first crimp. Reinsert the terminal.
14. Secure the secondary lock. Both sides of the connector must latch.

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COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
OFF-HIGHWAY SPEED SENSOR AND SOLDERED CANNON CONNECTORS
Part Numbers
Main Connector

23046469

Speed Sensor Pickup Connector

23046470

Lockup Connector

23046471

Trim Boost or Low-Low Connector

23046472

Trim Boost or Low-Low Internal

Harness Connector

23046475

Main Internal Harness Connector

23046476

Intermediate Two-Piece Harness

Connector, ECU Side

23046587

Intermediate Two-Piece Harness

Connector, Transmission Side

23046588

Special Tools
50-70% Tin Resin Core Solder, 18-20 SWG (0.036 to 0.040 Inch)
Pen Type Soldering Iron With Tip No Larger Than 1/8 Inch (Max 60W)
Desoldering Braid
NOTE:

Proper solder, equipment, techniques and cleanliness are important to achieve a good solder
joint. Before beginning any desoldering or soldering, tin the tip of the soldering iron and be
certain all dirt, grease and oil are cleaned from the connector and terminals being soldered.
Always heat the piece onto which the solder is to flow. Heating only the solder so it melts without
properly heating the piece(s) to be soldered will result in a cold solder joint and intermittent
continuity problems. Do not apply too much solder to a stranded wire since the solder will wick
up the wire and possibly cause wire breakage at the point where the solder stops. Do not use acid
core solder.

Procedures
A. Wire Removal (Desoldering)
1. Unscrew the back shell of the connector. Slide the back shell away from the connector.
2. Use a small screwdriver to lift the grommet away from the connector. Slide the grommet away from the
connector far enough to allow access to the terminals and wire ends. This may require some petroleum
jelly on the wire insulation and also the movement of some of the harness covering to allow enough
clearance between the grommet and connector.
3. Place the desoldering braid (wick) on top of the soldered joint of the terminal cup and wire. Place the
soldering iron on top of the desoldering braid and leave in place until solder wicks up the braid and the
wire can be removed.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
OFF-HIGHWAY SPEED SENSOR AND SOLDERED CANNON CONNECTORS (CONTD)
4. Repeat as necessary for other wires on the connector.
5. Remove the wire(s) from the grommet.
B. Soldering Wire Into Terminal
NOTE:

Wire(s) and terminal(s) should be free of dirt and grease. If a new connector is being installed on
a harness, be sure the back shell is in place before wires are inserted through the grommet.

1. Strip approximately .30 ( .030) inch (8.0 0.8 mm) of insulation from the wire.
2. Tin the stripped end of the wire.
3. Insert the wire through the proper grommet position.
NOTE:

Use petroleum jelly only if necessary and only on the wire insulation. Any petroleum jelly on the
tinned wire must be thoroughly cleaned off the wire or soldering will be impossible.

4. With the connector in a holding fixture at a 45 degree angle, apply heat with the soldering iron to the side
of the cup terminal while holding the solder in the cup. Heat the cup until the solder flows. If a new
connector is being used, begin soldering at the bottom center connection and work up and out from there.
5. Slowly feed solder into the cup until it is approximately half full. Remove the solder before removing the
heat. All solder cups being used should be pre-filled prior to inserting wires.
NOTE:

Feed solder slow enough to prevent a gas pocket of flux from forming. This will give a false fill. A
false fill can be corrected with additional heat and solder.

NOTE:

Total soldering time of steps 6 through 8 should be less than 5 seconds per terminal. If twenty or
more terminals are being soldered in one connector, allow the work to cool after half of the
terminals are soldered.

6. Start at the lowest cup and apply heat to the side of the cup until solder melts.
7. Insert the wire lead into the cup carefully, noting that the end of the wire is bottomed in the cup with
proper insulation clearance (approximately 1/16, or 0.0625, inch).

C-20

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
OFF-HIGHWAY SPEED SENSOR AND SOLDERED CANNON CONNECTORS
8. Maintain heat until the solder has properly flowed in the cup and on the wire. Overheating can cause
wicking of the solder in the stranded wire.
9. A good soldered connection will show a minimum amount of solder. Strands of the wire will be clearly
outlined in the joint. The joint will be completely covered with solder. The fillets will be a smooth, even
contour. The edges will be feathered, and the joint has a bright, smooth, clean appearance. Too little
solder is better than too much. If solder wicks up the wire, there will be a possibility of wire breakage at
the point where the solder stops.
10. When all connections are soldered and inspected, clean the connector with a contact cleaner to remove
the flux residue.
11. Slide the grommet into place and screw the back shell into place. On chassis harness connectors, tighten
the clamp on the connector back shell.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
REPAIRING A BROKEN WIRE
Part Numbers
14 to 16 AWG Splice

23046604

18 to 22 AWG Splice

23046605

Special Tools
Heat Gun

J25070 (or equivalent)

Crimping Tool

Appropriate for pre-insulated splice crimp

Wire Strippers

Applicable to wire size

Procedures
NOTE:

Each splice must be properly crimped and then heated to shrink the covering. This protects and
insulates the splice. Insulation piercing splice clips should not be used.

1. Locate the damaged wire. Cut the wire to eliminate the damaged area. If necessary, wire can be added to
the harness. Use the same size wire and, if possible, use the same color wire. When adding wire, two
splices must be installed using the following procedures.
2. Strip 0.3 inch (8.0 mm) of insulation from the ends of both wires being spliced.

3. Insert the wires into the splice crimp barrels.

4. Crimp both ends of the splice. Gently pull on the wires to ensure a good crimp.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
REPAIRING A BROKEN WIRE (CONTD)
5. Heat the splice with a heat gun until the covering shrinks and adhesive flows from both ends.

6. The splice is now sealed and insulated. Electrical tape is not necessary and should not be used.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
REPAIRING A TWISTED SHIELDED WIRE
Part Numbers
14 to 16 AWG Splice

23046604

18 to 22 AWG Splice

23046605

Special Tools
Heat Gun

J25070 (or equivalent)

Crimping Tool

Appropriate for pre-insulated splice crimp

Wire Strippers

Applicable to wire size

Procedures
1. Remove the wires outer jacket.

2. Unwrap the aluminum/mylar tape. Do not cut the tape off.

3. Untwist the wires. Cut the wires to eliminate the damaged area. If necessary, wire can be added to the
harness. Use the same size wire and, if possible, use the same color wire. When adding wire, two splices
must be installed using these procedures. Strip 0.3 inch (8.0 mm) of insulation from each main harness
wire being repaired.
NOTE:

C-24

If the drain wire is damaged, it should be repaired after the main harness wires are repaired.
This allows the main harness wires to be re-wrapped with aluminum/mylar tape prior to
finishing the repair.

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX C CONNECTOR, TERMINAL, AND WIRE REPAIR
REPAIRING A TWISTED SHIELDED WIRE (CONTD)
4. Insert the wires into the splice crimp barrels.

5. Crimp both ends of each splice. Gently pull on the wires to ensure a good crimp.

6. Heat each splice with a heat gun until the covering shrinks and adhesive flows from both ends.

7. Re-wrap the main harness wires with the aluminum/mylar tape. If necessary, repair the drain wire using
the procedures covered here. When finished, cover the repaired area with electrical tape.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX D ADDITIONAL TERMINAL DESIGNATIONS
Contents

Page

Diagnostic Data Link (DDL) Connector............................................................................................................ D-2

Two-Piece Chassis Harness Intermediate Connectors ....................................................................................... D-3
Amerline Cab Harness Interface Connector ...................................................................................................... D-4
AMP Cab Harness Interface Connector............................................................................................................. D-5
NOTE:

All other connector terminal designations are illustrated in Appendix A, Troubleshooting Steps Trouble Codes Present.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX D ADDITIONAL TERMINAL DESIGNATIONS
DIAGNOSTIC DATA LINK (DDL) CONNECTOR

Cavity
A
B
C
D
E
F
G
H
J
K
L
M

D-2

Circuit No.

Wire Color

Circuit

210
216

207

202B

236

Black
Yellow

Blue

Red

Yellow

DDL Ground
Enable
Not Used
Not Used
Data
Not Used
Not Used
12V Power
Not Used
Not Used
Not Used
Not Used
Spare to J1A

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX D ADDITIONAL TERMINAL DESIGNATIONS
TWO-PIECE CHASSIS HARNESS INTERMEDIATE CONNECTORS

B
G
N
W

M
V

E
L

U
b

D
J

S
Z

C
H

R
Y

H
P

J
S

B
E

Terminal

K
T

F
L

T
Z

U
a

N
V

b
g

G
M

W
c

h
k

TWOPIECE CHASSIS HARNESS,

SOCKET CONNECTOR

TWOPIECE CHASSIS HARNESS,

PLUG CONNECTOR

SOCKET CONNECTOR

PLUG CONNECTOR

Circuit No.

Wire Color

A
101
Red
B
102
Green
C
103
Violet
D

F
105
Violet
G
125
White
H
107
Green
J
112
White
K

M
113
Black
N
110
White
P
111
Green
R
108
Yellow
S

V
109
Blue
W
114
White
X
115
Green
Y
116
Yellow
Z

b
117
Black
c
118
Blue
d
119
Red
e
106
Black
f

g
104
Yellow
h
124
Red
j
120
Blue
k
123

l
121
Red
m
122
Violet
*Models with Lock-in-Range.

Description
Solenoid K + Lockup
Solenoid K - Lockup
Temperature Sensor
Plug
Plug
Solenoid(s) H- , I-* DP 8000, Solenoid J- CLBT 9000
Solenoid H+ DP 8000, Solenoid J+ CLBT 9000
Solenoid I+* DP 8000
Speed Sensor High
Plug
Plug
Speed Sensor Low
Solenoid G+*
Solenoid F+
Sodenoid EPlug
Plug
Plug
Solenoid D+
Solenoids B+, E+
Solenoid A+*
Solenoid(s) A-*, DPlug
Plug
Solenoids B-, CSolenoid G-*
Solenoid FThrottle Sensor/Semperature Sensor Ground
Plug
Throttle Sensor Out
Throttle Sensor High
Spare
Speed Sensor Shield
Spare
Spare

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX D ADDITIONAL TERMINAL DESIGNATIONS
AMERLINE CAB HARNESS INTERFACE CONNECTOR

Terminal

D-4

Circuit No.

Wire Color*

A
B
C
D
E
F
G
H
J
K
L
M
N
P
Q
R
S
T
U

223A
202A
203

225
231
208
209
217
211
234
213
214
215
216A
235
205
230

Red
Red
Blue

Violet
Blue
Black
Black
Violet
Yellow
Black
Blue
White
Violet
Yellow
White
Green
Yellow

233

Green

Circuit
12V ECU Power
12V ECU Power
Cont. Power Memory

12V Ignition to Selector

Neutral Start
Ground Battery Negative
Ground Battery Negative
2-Speed Governor
Retarder In
Lamp Ground 12V/24V
Retarder Out
Reverse
CHECK TRANS Out
Test Switch
12V Not Used (24V Ignition)
Speedometer
12V Selector Lamp Ground
(24V Selector Lamp Dimmer)
12V Selector Lamp Dimmer
(24V Not Used)

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX D ADDITIONAL TERMINAL DESIGNATIONS
AMP CAB HARNESS INTERFACE CONNECTOR

Terminal

Circuit No.

Wire Color*

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19

223A
202A
203

225
231
208
209
217
211
234
213
214
215
216A
235
205
230

Red
Red
Blue

Violet
Blue
Black
Black
Violet
Yellow
Black
Blue
White
Violet
Yellow
White
Green
Yellow

20

233

Green

21
22
23
24

Circuit
12V ECU Power
12V ECU Power
Cont. Power Memory

12V Ignition to Selector

Neutral Start
Ground Battery Negative
Ground Battery Negative
2-Speed Governor
Retarder In
Lamp Ground 12V/24V
Retarder Out
Reverse
CHECK TRANS Out
Test Switch
12V Not Used (24V Ignition)
Speedometer
12V Selector Lamp Ground
(24V Selector Lamp Dimmer)
12V Selector Lamp Dimmer
(24V Not Used)
Not Used
Not Used
Not Used
Not Used

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS
Contents

Page

MTB 600/HTB 700 4-Speed Electronic Control System - Schematic View .............................................. E-3
HTB/CLT/CLBT 700 5-Speed Electronic Control System - Schematic View ........................................... E-4
CLBT 5962/6062 (Lock-to-Neutral) Electronic Control System - Schematic View .................................. E-5
CLBT 5962/6062 (Lock-in-Range) Electronic Control System - Schematic View .................................... E-6
DP 8963 (Lock-to-Neutral) Electronic Control System - Schematic View ................................................ E-7
DP 8963 (Lock-in-Range) Electronic Control System - Schematic View .................................................. E-8
CLBT 9681 (Lock-in-Range) Electronic Control System - Schematic View ............................................. E-9/E-10
AS00-132 Plus II Wiring Guide (Sheet 1)................................................................................................... E-11
AS00-132 Plus II Wiring Guide (Sheet 2)................................................................................................... E-13
AS00-080 Model 5/6/8/9000 Series Plus II Wiring Guide (Sheet 1) .......................................................... E-15
AS00-080 Model 5/6/8/9000 Series Plus II Wiring Guide (Sheet 2) .......................................................... E-17
AS00-134 Plus II Installation Requirements (Sheet 1) ............................................................................... E-19
AS00-134 Plus II Installation Requirements (Sheet 2) ............................................................................... E-21
AS00-078 Model 5/6/8/9000 Series Plus II Installation Requirements (Sheet 1)....................................... E-23
AS00-078 Model 5/6/8/9000 Series Plus II Installation Requirements (Sheet 2)....................................... E-25

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS
The schematics in this Appendix illustrate the interface connections for the transmission electronic control
system. Some wiring schematics are shared by more than one transmission model; therefore, the schematics in
this section are grouped according to transmission series.
The schematic views are abbreviated schematics that show the beginning and ending connections for each wire
within the electronic control system. They are easier to use than the more detailed wiring guides, which show the
entire diagram and how each wire is traced through the system.
The installation requirements drawings show the connections between the electronic control system and other
vehicle components. At the end of this section are wiring schematics for the different wiring harnessescab,
chassis (on and off-highway), and secondary mode.
Contents

Page

V 731 Transmission:
Schematic ViewV 731 3-Speed Electronic Control System ........................................................................... E-3
Wiring GuideSealed Standard Electronic Control (AS00-081) ...................................................................... E-5
Installation RequirementsSealed Standard Electronic Control (AS00-138 Sheet 1) ...................................... E-7
Installation RequirementsSealed Standard Electronic Control (AS00-138 Sheet 2) ...................................... E-9
MT(B)/HT(B) 600/700 Transmissions:
Schematic ViewMTB 600/HTB 700 4-Speed Electronic Control System...................................................... E-11
Schematic ViewHTB/CLT/CLBT 700 5-Speed Electronic Control System................................................... E-12
Wiring GuidePlus II Electronic Control (AS00-132 Sheet 1)......................................................................... E-13
Wiring GuidePlus II Electronic Control (AS00-132 Sheet 2)......................................................................... E-15
Installation RequirementsPlus II Electronic Control (AS00-134 Sheet 1)...................................................... E-17
Installation RequirementsPlus II Electronic Control (AS00-134 Sheet 2)...................................................... E-19
CLBT 5000/6000, DP 8000, CLBT 9000 Off-Highway Transmissions:
NOTE:

Off-highway transmissions use two different valve bodies: lock-to-range (standard for
most vehicles) and fail-to-neutral (for stationary applications, i.e., drilling and pumping).
The following schematic views represent configurations for each valve body type
(12-volt systems).

Schematic ViewCLBT 5962/6062 Electronic Control System, Lock-in-Range............................................. E-21

Schematic ViewDP 8963 Electronic Control System, Lock-in-Range ........................................................... E-22
Schematic ViewCLBT 9681 Electronic Control System, Lock-in-Range ...................................................... E-23
Schematic ViewCLBT 5962/6062 Electronic Control System, Lock-to-Neutral ........................................... E-24
Schematic ViewDP 8963 Electronic Control System, Lock-to-Neutral ......................................................... E-25
COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS
Contents

Page

CLBT 5000/6000, DP 8000, CLBT 9000 Off-Highway Transmissions (contd):

Wiring GuidePlus II Electronic Control (AS00-080 Sheet 1)......................................................................... E-27
Wiring GuidePlus II Electronic Control (AS00-080 Sheet 2)......................................................................... E-29
Installation RequirementsPlus II Electronic Control (AS00-078 Sheet 1)...................................................... E-31
Installation RequirementsPlus II Electronic Control (AS00-078 Sheet 2)...................................................... E-33
Harnesses:
Schematic ViewCab Harness........................................................................................................................... E-35
Schematic ViewChassis Harness, On-highway............................................................................................... E-36
Schematic ViewChassis Harness, Off-highway .............................................................................................. E-37
Schematic ViewSecondary Harness ................................................................................................................ E-38
Wiring GuideSealed Cab Harness (AS00-154) ............................................................................................... E-39
Wiring GuidePlus II Chassis Harness, On-Highway (AS00-053) .................................................................. E-41
Wiring GuidePlus II Chassis Harness, Off-Highway (AS00-079).................................................................. E-43
Wiring GuidePlus II Secondary Mode Harness (AS00-155) .......................................................................... E-45

E-2

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS

V 731 Transmission Electronic Control System

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS
Schematic View

MT(B) 600 or HT(B) 700 4-Speed Transmission Electronic Control System

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS
Schematic View

HT(B) or CLT, CLBT 700 5-Speed Transmission Electronic Control System

E-12

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS
Schematic View

CLBT 5962/6062 Lock-in-Range (12 Volt System)

COPYRIGHT 1994 GENERAL MOTORS CORP.

E-21

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS
Schematic View

DP 8963 Lock-in-Range (12 Volt System)

E-22

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS
Schematic View

CLBT 9681 Lock-in-Range (12 Volt System)

COPYRIGHT 1994 GENERAL MOTORS CORP.

E-23

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS
Schematic View

CLBT 5962/6062 Lock-to-Neutral (12 Volt System)

E-24

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS
Schematic View

DP 8693 Lock-to-Neutral (12 Volt System)

COPYRIGHT 1994 GENERAL MOTORS CORP.

E-25/E-26

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS

COPYRIGHT 1994 GENERAL MOTORS CORP.

E-35

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS

E-36

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS

COPYRIGHT 1994 GENERAL MOTORS CORP.

E-37

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX E ELECTRICAL SCHEMATICS

E-38

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX F HYDRAULIC SCHEMATICS
Model

Page

V 731 3-Speed Hydraulic Schematic, Neutral Operation .................................................................................... F-3

MT 600 or HT 700 4-Speed Hydraulic Schematic, Neutral Operation................................................................ F-5
HT(B) 700 or CLT, CLBT 700 5-Speed Hydraulic Schematic, Neutral Operation ............................................. F-7
CLBT 5962/6062 Hydraulic Schematic, Neutral Operation ................................................................................ F-9
DP 8963 Hydraulic Schematic, Neutral Operation.............................................................................................. F-11
CLBT 9681 Hydraulic Schematic, Neutral Operation ........................................................................................ F-13

NOTE:

These schematics represent typical on-highway and off-highway applications. Refer to the
appropriate Service Manual for specific application schematics.

COPYRIGHT 1994 GENERAL MOTORS CORP.

F-1 / F-2

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX G SPECIAL TOOLS
Tool Number

Description

J25563

Cutter/Crimper Pliers

J28742-A

Weather Pac II Terminal Remover

J33095

Harness Terminal Remover

J34182

Transmission Pin Connector Crimper

J34513

Transmission Connector Terminal Remover

J34517

Transmission Housing Breakout Cable

J34521

Jumper Wire Set

J34823

AMP Pin Remover

22S1543

Field Modification Kit For Kent-Moore/Aidco Valve Body Test Stand

(HTB/CLT, CLBT 700)

22S1554

Cart-Update For Transmission Test Stands (Aidco)

22S1773

Field Modification Kit For Kent-Moore/Aidco Valve Body Test Stand (MTB 600)

53-K055

Update Kit For Hicklin Transmission Test Stand (Hicklin GM Power)

4992

DDL Reader Tool (Micro Processor Systems, Inc.

52270

DDL Monitor (Owatonna Tool Company)

J21757-03

Pressure Switch Wrench (Without Wire Extensions), Clamp-Down Assembly

J25070

Heat Gun

J33884

Pressure Switch Gage Tester

J3384-10

Pressure Switch Gage Tester, Bolt Down Solenoid Adapter Kit

J34029-15

EZ Mini-Hook Test Lead Set

J34520

High Impedance Digital Multimeter Kit

J34525

Display Data Line Scanner (Kent-Moore)

J34988

Torx Bit Set (Bolt Down Solenoid/Pressure Switches)

J35123

Crimping Pliers

J35606

Weather-Pac Terminal Crimper

J35689

Terminal Remover Metri-Pack

J35751

Jumper Wire Kit

J35813

J1A/J1B Breakout Connector

J35814

J3 Breakout Connector

J35980

Off-Highway Transmission Breakout Harness

J35889

PROM Remover

J36105

Pressure Switch Wrench (With Wire Extensions), Clamp-Down Assembly

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX G SPECIAL TOOLS
VENDOR ADDRESSES
Aidco
800 Liberty Street
Adrian, Michigan 49221
Phone: 517-265-7165

Micro Processor Systems, Inc.

7641 Nineteen Mile Road
Sterling Heights, MI 48078
Phone: 313-731-6410

Hicklin GM Power Co., Inc.

Interstate Highways 80 & 35
At 2nd Avenue
Des Moines, Iowa 50333
Phone: 515-286-4800

Owatonna Tool Company

Major Motors Division
655 Eisenhower Drive
Owatonna, Minnesota 55060
Phone: 800-533-0492

Kent-Moore Heavy Duty Division

Sealed Power Corporation
29784 Little Mack
Roseville, MI 48066-2298
Phone: 313-774-9500

Allison Transmission believes these sources and tools to be reliable. There may be additional manufacturers of
such tools. Allison Transmission does not endorse, indicate any preference for, or assume any responsibility for
the products or tools from these firms, or for any such items which may be available from other sources.

G-2

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION
Contents

Page

Diagnostic Codes and System Response. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-3

Description of Individual Codes and System Response
Code 12 Low Lube Pressure/Low Oil Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-4
Code 13 Low Battery Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-4
Code 14 Forward Direction Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-5
Code 15 Reverse Direction Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-5
Code 21 Throttle Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-6
Code 22 Speed Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-7
Code 23 Primary Shift Selector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-7
Code 24 Transmission Oil Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-8
Code 31 Secondary Shift Selector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-9
Code 32 Wrong Direction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-9
Code 33 Oil Temperature Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-10
Code 34 PROM Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-10
Code 41 (On-Highway) Latching Solenoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-11
Code 41 (Off-Highway) Solenoid A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-12
Code 42 (On-Highway) Latching Solenoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-13
Code 42 (Off-Highway) Solenoid B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-14
Code 43 (On-Highway) Latching Solenoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-15
Code 43 (Off-Highway) Solenoid C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-16
Code 44 (On-Highway) Latching Solenoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-17
Code 44 (Off-Highway) Solenoid D. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-18
Code 45 (On-Highway) Latching Solenoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-19
Code 45 (Off-Highway) Solenoid E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-20
Code 46 (On-Highway) Latching Solenoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-21

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION
Contents

Page

Code 51 Non-Latching Solenoids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-22

Code 51 (K) Solenoid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-22
Codes 51 and 52 Non-Latching Solenoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-23
Code 52 (H) Solenoid (DP 8000) or (J) Solenoid (CLBT 9000). . . . . . . . . . . . . . . . . . . . . . . . . . . H-23
Code 53 Neutral/Range Solenoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-24
Code 53 (I) Solenoid (DP 8000). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-24
Code 54 Latching Solenoid Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-25
Code 54 Solenoid Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-25
Code 61 (G) Solenoid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-26
Code 62 (F) Solenoid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-26
Code 63 (G) Solenoid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-27
Code 66 Transmission Engine Communication Link (TECL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-27
Code 69 Computer Malfunction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H-28

H-2

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION
DIAGNOSTIC CODES AND SYSTEM RESPONSE
Code
12
13
14
15
21
22
23
24

31
32
33
34
41

42

43

44

45

46

51
52
53
54
66
69

DO NOT
SHIFT
Light

Description
Low fluid pressure/level
Low input voltage: (in neutral)
(in range)
Forward pressure switch
Reverse pressure switch
Throttle sensor, in error zone
Speed sensor
Primary shift selector
Fluid temperature:
Cold (below -32C)
Cool (-32 to -7C)
Hot (above 132C)
Secondary shift selector
Wrong direction signal
Temp sensor, in error zone
PROM check
J solenoid (neutral) on test:
Below 1200 output rpm
Above 1200 output rpm
F solenoid (fwd/rev) on test:
Below 1200 output rpm
Above 1200 output rpm
D solenoid on test:
Below 1200 output rpm
Above 1200 output rpm
C solenoid on test:
Below 1200 output rpm
Above 1200 output rpm
B solenoid on test:
Below 1200 output rpm
Above 1200 output rpm
A solenoid on test:
Below 1200 output rpm
Above 1200 output rpm
G solenoid (lockup)
E solenoid (trim boost)
H solenoid (neutral): on test
Off test
A, B, C, D, F, and J solenoids:
Off test
Transmission engine
Communication link
Electronic control unit test

Transmission Response

Clearing CHECK
TRANS Light

Off
On
Off
Off
Off
Off
On
Off

Inhibits high gear

Hold in neutral
May not shift
Normal operation
Normal operation
Full throttle assumed
Drop LU and hold in gear
Hold in last range*

Next valid lube

Acceptable volts
Not turned on
Next valid signal
Next valid signal
ECU power off/on
ECU power off/on
Next valid range

On
Off
Off
Off
Off
Off
On

Hold in neutral
Inhibits upshifts
Inhibits high gear
Hold in last range*
Shift to neutral
Normal operation
Drop LU and hold in gear

Temp above -32C

Not turned on
Temp below 132C
Next valid range
Select neutral
Next valid temp
ECU power off/on

Off
On

May not shift

Drop LU and hold in gear

ECU power off/on

ECU power off/on

Off
On

May not shift

Drop LU and hold in gear

ECU power off/on

ECU power off/on

Off
On

May not shift

Drop LU and hold in gear

ECU power off/on

ECU power off/on

Off
On

May not shift

Drop LU and hold in gear

ECU power off/on

ECU power off/on

Off
On

May not shift

Drop LU and hold in gear

ECU power off/on

ECU power off/on

Off
On
Off
Off
Off
On

May not shift

Drop LU and hold in gear
Possible loss of lockup
Possible full trim boost
May not shift
Drop LU and hold in gear

ECU power off/on

ECU power off/on
Valid signal
Valid signal
ECU power off/on
ECU power off/on

On
Off

Drop LU and hold in gear

Fixed throttle assumed
Fixed engine rpm assumed
Drop LU and hold in gear

ECU power off/on

On

Next valid signal

ECU power off/on

NOTES: (1) For all errors, the CHECK TRANS light will illuminate immediately.
(2) Except for codes 22 and 69, lockup clutch will not be dropped until the retarder
or compression brake (if used) shuts off.
(3) Engine restart will usually turn ECU power off/on.
*Shifting may still occur within that gear range.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code
12

DO NOT
SHIFT
Light

Description
Low fluid pressure/level

Off

Clearing CHECK
TRANS Light

Transmission Response
Inhibits high gear

Next valid lube

CODE 12 LOW LUBE PRESSURE/LOW OIL LEVEL

A low lube pressure (low oil level) diagnostic code can be set in memory if all of the following conditions
are satisfied:
1. (2 minutes) have expired since turn on.
2. (7 seconds) have expired since last shift.
3. (7 seconds) have expired since last converter to lockup mode change.
4. (7 seconds) have expired since last lockup to converter mode change.
5. Throttle position is greater than (60%).
6. Transmission is in forward.
7. Turbine speed in each range is greater than (1200 rpm).
When the listed conditions are satisfied and a low pressure (low oil level) condition is sensed, the
CHECK TRANS light will come on.
The light will go off when conditions 1 through 4 and 6 are satisfied and there is proper lube pressure
(oil level) signal.
NOTE: Item in parenthesis may be different per calibration PROM you have.

Code

DO NOT
SHIFT
Light

Description

Clearing CHECK
TRANS Light

Transmission Response

Low input voltage: in neutral

On

Hold in neutral

Acceptable volts

Low input voltage: in range

Off

May not shift

Not turned on

13

CODE 13 LOW BATTERY VOLTAGE

There are two situations when a low battery voltage diagnostic code can set in memory.

Transmission is in neutral
When in this situation, the CHECK TRANS and DO NOT SHIFT lights will come on. If forward or reverse
are requested, the shift will not occur.
The light will go off and normal operation will resume if neutral is selected and proper voltage is detected.

Transmission is in reverse or forward

When in this situation and a shift is made, a code will be set in memory no lights come on.
If satisfactory battery is detected, Code 13 will be cleared from memory.
H-4

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION
Code
14

DO NOT
SHIFT
Light

Description
Forward pressure switch

Off

Transmission Response
Normal operation

Clearing CHECK
TRANS Light
Next valid signal

CODE 14 FORWARD DIRECTION SIGNALS

A forward direction switch diagnostic code can be set in memory if one of the following conditions exists:
1. Both direction signals present in reverse.
2. No direction signals present while in forward and throttle greater than (60%).
If one of the conditions exists, the CHECK TRANS light will come on.
The CHECK TRANS light will go off when a valid direction signal is detected.
NOTE: Item in parenthesis may be different per calibration PROM you have.

Code
15

DO NOT
SHIFT
Light

Description
Reverse pressure switch

Off

Transmission Response
Normal operation

Clearing CHECK
TRANS Light
Next valid signal

CODE 15 REVERSE DIRECTION SWITCH

A reverse direction switch diagnostic code can be set in memory if one of the following conditions exist:
1. Both direction signals present in forward.
2. No direction signals present while in reverse and throttle greater than (60%).
If one of the conditions exists, the CHECK TRANS light will come on.
The CHECK TRANS light will go off when a valid direction signal is detected.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION
Code
21

DO NOT
SHIFT
Light

Description
Throttle sensor, in error zone

Off

Clearing CHECK
TRANS Light

Transmission Response
Full throttle assumed

ECU power off/on

CODE 21 THROTTLE SENSOR

A throttle sensor diagnostic code can be set in memory if the throttle counts are in either of the error zones
(Figure H-1).

THROTTLE COUNTS

255

Stroke
Approx 34

233
Idle

Error
Zone

14
WOT

.2

0
Error
Zone

1.8

1.9
Code 21.art

Figure H-1. Stroke of Throttle Sensor

When an extreme stroke condition is detected, the CHECK TRANS light comes on. The throttle percent is set
to 100% or 0% depending on usage. Therefore, you may get either closed throttle shift points or full throttle shift
points when this code is present.
To clear this situation, the input power must be shut off and then back on, and throttle counts proper.

H-6

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code
22

DO NOT
SHIFT
Light

Description
Speed sensor

On

Transmission Response
Drop LU and hold in gear

Clearing CHECK
TRANS Light
ECU power off/on

CODE 22 SPEED SENSOR

A speed sensor diagnostic code can be set in memory if any of the following conditions exist:
1. If there is an abnormal problem with speed sensor continuity.
2. Speed in excess of 7680 rpm.
3. Unusually rapid deceleration.
If any of the conditions are present, the CHECK TRANS and DO NOT SHIFT lights will come on. All shifts
will be blocked and lockup will be dropped.
To clear this situation, the input power must be shut off and then back on.

Code
23

DO NOT
SHIFT
Light

Description
Primary shift selector

Off

Transmission Response
Hold in last range*

Clearing CHECK
TRANS Light
Next valid range

CODE 23 PRIMARY SHIFT SELECTOR

A shift selector diagnostic code can be set in memory if either of the following conditions is not satisfied:
1. The switch coding must match a preset coding.
2. The switch coding must be legitimate.
If either of the conditions is not met, the CHECK TRANS light will come on. The last good command from the
shift selector will be used.
When conditions 1 and 2 are correct, the CHECK TRANS light will go out.

*Shifting may still occur up to and including the range selected.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION
Code

24

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

Fluid temperature: cold

On

Hold in neutral

Temp above -32C

Fluid temperature: cool

Off

Inhibits upshifts

Not turned on

Fluid temperature: hot

Off

Inhibits high gear

(on-highway)

Temp below 132C

Fluid temperature: hot

Off

Inhibits high gear (5th, 6th)

(off-highway)

Temp below 250F

CODE 24 TRANSMISSION OIL TEMPERATURE

Oil temperature which is not within normal operating range [above 20F (-7C)] and at or below [270F (132C)]
will cause three possible effects.

Block shifting operation between [-100F (-73C) and -25F (-32C)]

1. CHECK TRANS and DO NOT SHIFT lights are on. Range shifts are blocked, but no code is set.
2. Warming oil above [-25F (-32C)] will allow limited shifting.

Limited shifting operation in range of [-25F (-32C) and -20F (-7C)]

1. A hold is placed on all range changes, but no code is set.
2. Warming oil above [20F (-7C)] will allow normal shifting.

Overheat operation between [270F (132C) and 350F (204C)]

1. CHECK TRANS light is on and code is set in memory.
2. Cooling oil to [270F (132C)] or below will turn light off.
NOTE: Items in brackets may be different per the calibration PROM that you have.

H-8

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code
31

DO NOT
SHIFT
Light

Description
Secondary shift selector

Off

Transmission Response
Hold in last range*

Clearing CHECK
TRANS Light
Next valid range

CODE 31 SECONDARY SHIFT SELECTOR

A shift selector diagnostic code can be set in memory if either of the following conditions is not satisfied:
1. The switch coding must match a preset coding.
2. The switch coding must be legitimate.
If either of the conditions is not met, the CHECK TRANS light will come on. The last good command from the
shift selector will be used.
When conditions 1 and 2 are correct, the CHECK TRANS light will go out.

*Shifting may still occur up to and including the range selected.

Code
32

DO NOT
SHIFT
Light

Description
Wrong direction signal

Off

Transmission Response
Shift to neutral

Clearing CHECK
TRANS Light
Select neutral

CODE 32 WRONG DIRECTION

A wrong direction diagnostic code will be set in memory if one of the following conditions exist:
1. If reverse pressure signal in forward range but no forward pressure, after (2 seconds).
2. If forward pressure signal in reverse range but no reverse pressure, after (2 seconds).
3. If forward or reverse or both pressure signals in neutral, after (2 seconds).
If one of the conditions exists, the CHECK TRANS light will come on. The transmission will shift to neutral.
This condition will clear when the shift selector is moved to a new direction. If the situation is corrected, the
CHECK TRANS light will also go off.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code
33

Description
Temp sensor, in error zone

DO NOT
SHIFT
Light
Off

Transmission Response
Normal operation

Clearing CHECK
TRANS Light
Next valid temp

CODE 33 OIL TEMPERATURE SENSOR

An oil temperature sensor diagnostic code will be set in memory if the oil temperature is greater than [350 F
(204C)] or less than [-100F (-73C)].
If this condition exists, the CHECK TRANS light will go out.
NOTE: Items in brackets may be different per the calibration PROM you have.

Code
34

Description
PROM check

DO NOT
SHIFT
Light
ON

Transmission Response
Drop LU and hold in gear

Clearing CHECK
TRANS Light
ECU power off/on

CODE 34 PROM CHECK

A PROM diagnostic code will be set in memory if either of the following conditions occur:
1. The PROM is not in its socket.
2. The PROM is faulty.
If one of these conditions exists, the CHECK TRANS and DO NOT SHIFT lights will turn on. Lockup will
be dropped and all shifts blocked.
To clear the conditions, the input power must be shut off and turned back on again. If conditions 1 or 2 do not
occur, normal operation will then be resumed.

H-10

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

On-Highway

41

J solenoid on test:
Below 1200 output rpm

Off

May not shift

ECU power off/on

Above 1200 output rpm

On

Drop LU and hold in gear

ECU power off/on

CODES 41, 42, 43, 44, 45, 46 LATCHING SOLENOIDS

A solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. The resistance between the two wires to a solenoid is too high or too low.
2. The resistance is too low between either of the two wires and ground.
If one of the conditions exists at an output speed over 1200 rpm, the CHECK TRANS and the DO NOT
SHIFT lights will come on. Lockup will be dropped and shifting will be blocked.
NOTE: Lockup will be dropped unless the retarder is applied.
If the output speed is below 1200 rpm, shifts are not blocked and the DO NOT SHIFT light does not come on.
Only the CHECK TRANS light comes on.
To clear the conditions, the following must be done:
To resume normal shifting, reduce output speed below 1200 rpm.
To clear CHECK TRANS light, input power must be shut off and turned back on.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

Off-Highway

41

A solenoid on test:
Below 500 output rpm

Off

May not shift

ECU power off/on

Above 500 output rpm

On

Drop LU and hold in gear

ECU power off/on

CODES 41, 42, 43, 44, 45, 61 SOLENOIDS A, B, C, D, E, G

A solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. Resistance between the two wires to a solenoid is too high or too low.
2. Resistance is too high or too low between either of the two wires and ground.
If one of the conditions exists at an output speed over 500 rpm, the CHECK TRANS and the DO NOT
SHIFT lights will come on. Lockup will be dropped and shifting will be blocked.
NOTE: Lockup will be dropped unless the retarder is applied.
If the output speed is below 500 rpm, shifts are not blocked and the DO NOT SHIFT light does not come on.
Only the CHECK TRANS light comes on.
To clear the conditions, the following must be done:
To resume normal shifting, reduce output speed below 500 rpm.
To clear CHECK TRANS light, the engine must be shut off and restarted and the conditions must not
be present.

H-12

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

On-Highway

42

F solenoid on test:
Below 1200 output rpm

Off

May not shift

ECU power off/on

Above 1200 output rpm

On

Drop LU and hold in gear

ECU power off/on

CODES 41, 42, 43, 44, 45, 46 LATCHING SOLENOIDS

A solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. The resistance between the two wires to a solenoid is too high or too low.
2. The resistance is too low between either of the two wires and ground.
If one of the conditions exists at an output speed over 1200 rpm, the CHECK TRANS and the DO NOT
SHIFT lights will come on. Lockup will be dropped and shifting will be blocked.
NOTE: Lockup will be dropped unless the retarder is applied.
If the output speed is below 1200 rpm, shifts are not blocked and the DO NOT SHIFT light does not come on.
Only the CHECK TRANS light comes on.
To clear the conditions, the following must be done:
To resume normal shifting, reduce output speed below 1200 rpm.
To clear CHECK TRANS light, input power must be shut off and turned back on.

COPYRIGHT 1994 GENERAL MOTORS CORP.

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APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

Off-Highway

42

B solenoid on test:
Below 500 output rpm

Off

May not shift

ECU power off/on

Above 500 output rpm

On

Drop LU and hold in gear

ECU power off/on

CODES 41, 42, 43, 44, 45, 61 SOLENOIDS A, B, C, D, E, G

A solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. Resistance between the two wires to a solenoid is too high or too low.
2. The resistance is too high or too low between either of the two wires and ground.
If one of the conditions exists at an output speed over 500 rpm, the CHECK TRANS and the DO NOT
SHIFT lights will come on. Lockup will be dropped and shifting will be blocked.
NOTE: Lockup will be dropped unless the retarder is applied.
If the output speed is below 500 rpm, shifts are not blocked and the DO NOT SHIFT light will come on.
To clear the above conditions, the following must be done:
To resume normal shifting, reduce output speed below 500 rpm.
To clear CHECK TRANS light, the engine must be shut off and restarted and the conditions must not
be present.

H-14

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

On-Highway

43

D solenoid on test:
Below 1200 output rpm

Off

May not shift

ECU power off/on

Above 1200 output rpm

On

Drop LU and hold in gear

ECU power off/on

CODES 41, 42, 43, 44, 45, 46 LATCHING SOLENOIDS

A solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. The resistance between the two wires to a solenoid is too high or too low.
2. The resistance is too low between either of the two wires and ground.
If one of the conditions exists at an output speed over 1200 rpm, the CHECK TRANS and the DO NOT
SHIFT lights will come on. Lockup will be dropped and shifting will be blocked.
NOTE: Lockup will be dropped unless the retarder is applied.
If the output speed is below 1200 rpm, shifts are not blocked and the DO NOT SHIFT light does not come on.
Only the CHECK TRANS light comes on.
To clear the conditions, the following must be done:
To resume normal shifting, reduce output speed below 1200 rpm.
To clear CHECK TRANS light, input power must be shut off and turned back on.

COPYRIGHT 1994 GENERAL MOTORS CORP.

H-15

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

Off-Highway

43

C solenoid on test:
Below 500 output rpm

Off

May not shift

ECU power off/on

Above 500 output rpm

On

Drop LU and hold in gear

ECU power off/on

CODES 41, 42, 43, 44, 45, 61 SOLENOIDS A, B, C, D, E, G

A solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. Resistance between the two wires to a solenoid is too high or too low.
2. The resistance is too high or too low between either of the two wires and ground.
If one of the conditions exists at an output speed over 500 rpm, the CHECK TRANS and the DO NOT
SHIFT lights will come on. Lockup will be dropped and shifting will be blocked.
NOTE: Lockup will be dropped unless the retarder is applied.
If the output speed is below 500 rpm, shifts are not blocked and the DO NOT SHIFT light will come on.
To clear the above conditions, the following must be done:
To resume normal shifting, reduce output speed below 500 rpm.
To clear CHECK TRANS light, the engine must be shut off and restarted and the conditions must not
be present.

H-16

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

On-Highway

44

C solenoid on test:
Below 1200 output rpm

Off

May not shift

ECU power off/on

Above 1200 output rpm

On

Drop LU and hold in gear

ECU power off/on

CODES 41, 42, 43, 44, 45, 46 LATCHING SOLENOIDS

A solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. The resistance between the two wires to a solenoid is too high or too low.
2. The resistance is too low between either of the two wires and ground.
If one of the conditions exist at an output speed over 1200 rpm, the CHECK TRANS and the DO NOT
SHIFT lights will come on. Lockup will be dropped and shifting will be blocked.
NOTE: Lockup will be dropped unless the retarder is applied.
If the output speed is below 1200 rpm, shifts are not blocked and the DO NOT SHIFT light does not come on.
Only the CHECK TRANS light comes on.
To clear the conditions, the following must be done:
To resume normal shifting, reduce output speed below 1200 rpm.
To clear CHECK TRANS light, input power must be shut off and turned back on.

COPYRIGHT 1994 GENERAL MOTORS CORP.

H-17

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

Off-Highway

44

D solenoid on test:
Below 500 output rpm

Off

May not shift

ECU power off/on

Above 500 output rpm

On

Drop LU and hold in gear

ECU power off/on

CODES 41, 42, 43, 44, 45, 61 SOLENOIDS A, B, C, D, E, G

A solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. Resistance between the two wires to a solenoid is too high or too low.
2. The resistance is too high or too low between either of the two wires and ground.
If one of the above conditions exists at an output speed over 500 rpm, the CHECK TRANS and the DO NOT
SHIFT lights will come on. Lockup will be dropped and shifting will be locked.
NOTE: Lockup will be dropped unless the retarder is applied.
If the output speed is below 500 rpm, shifts are not blocked and the DO NOT SHIFT light will come on.
To clear the above conditions, the following must be done:
To resume normal shifting, reduce output speed below 500 rpm.
To clear CHECK TRANS light, the engine must be shut off and restarted and the conditions must not
be present.

H-18

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

On-Highway

45

B solenoid on test:
Below 1200 output rpm

Off

May not shift

ECU power off/on

Above 1200 output rpm

On

Drop LU and hold in gear

ECU power off/on

CODES 41, 42, 43, 44, 45, 46 LATCHING SOLENOIDS

A solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. The resistance between the two wires to a solenoid is too high or too low.
2. The resistance is too high or too low between either of the two wires and ground.
If one of the conditions exist at an output speed over 1200 rpm, the CHECK TRANS and the DO NOT
SHIFT lights will come on. Lockup will be dropped and shifting will be blocked.
NOTE: Lockup will be dropped unless the retarder is applied.
If the output speed is below 1200 rpm, shifts are not blocked and the DO NOT SHIFT light does not come on.
Only the CHECK TRANS light comes on.
To clear the conditions, the following must be done:
To resume normal shifting, reduce output speed below 1200 rpm.
To clear CHECK TRANS light, input power must be shut off and turned back on.

COPYRIGHT 1994 GENERAL MOTORS CORP.

H-19

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

Off-Highway

45

E solenoid on test:
Below 500 output rpm

Off

May not shift

ECU power off/on

Above 500 output rpm

On

Drop LU and hold in gear

ECU power off/on

CODES 41, 42, 43, 44, 45, 61 SOLENOIDS A, B, C, D, E, G

A solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. Resistance between the two wires to a solenoid is too high or too low.
2. The resistance is too high or too low between either of the two wires and ground.
If one of the above conditions exists at an output speed over 500 rpm, the CHECK TRANS and the DO NOT
SHIFT lights will come on. Lockup will be dropped and shifting will be blocked.
NOTE: Lockup will be dropped unless the retarder is applied.
If the output speed is below 500 rpm, shifts are not blocked and the DO NOT SHIFT light will come on.
To clear the above conditions, the following must be done:
To resume normal shifting, reduce output speed below 500 rpm.
To clear CHECK TRANS light, the engine must be shut off and restarted and the conditions must not
be present.

H-20

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

On-Highway

46

A solenoid on test:
Below 1200 output rpm

Off

May not shift

ECU power off/on

Above 1200 output rpm

On

Drop LU and hold in gear

ECU power off/on

CODES 41, 42, 43, 44, 45, 46 LATCHING SOLENOIDS

A solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. The resistance between the two wires to a solenoid is too high or too low.
2. The resistance is too high or too low between either of the two wires and ground.
If one of the conditions exist at an output speed over 1200 rpm, the CHECK TRANS and the DO NOT
SHIFT lights will come on. Lockup will be dropped and shifting will be blocked.
NOTE: Lockup will be dropped unless the retarder is applied.
If the output speed is below 1200 rpm, shifts are not blocked and the DO NOT SHIFT light does not come on.
Only the CHECK TRANS light comes on.
To clear the conditions, the following must be done:
To resume normal shifting, reduce output speed below 1200 rpm.
To clear CHECK TRANS light, input power must be shut off and turned back on.

COPYRIGHT 1994 GENERAL MOTORS CORP.

H-21

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APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

On-Highway
51

G solenoid

Off

Possible loss of lockup

Valid signal

CODE 51 NON-LATCHING SOLENOIDS

A non-latching solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. The resistance between the two wires to a solenoid is too high or too low.
2. The resistance is too low between either of the two wires and ground.
If one of the conditions exists, the CHECK TRANS light will come on.
The CHECK TRANS light will go out when conditions 1 and 2 are eliminated.

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

Off-Highway
51

K solenoid

Off

Possible loss of lockup

CODE 51 (K) SOLENOID

A solenoid diagnostic code will be set in memory if one of the following exists:
1. Resistance in the circuit across the solenoid is too high or too low.
2. One of the two wires going to the solenoid is in contact with an external voltage.
3. One of the two wires going to the solenoid is shorted to ground.
4. Internal ECU switching problem.
If one of the above conditions exists, the CHECK TRANS light will come on.
The CHECK TRANS light will go out when the condition is corrected.

H-22

COPYRIGHT 1994 GENERAL MOTORS CORP.

Valid signal

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

On-Highway
52

E solenoid

Off

Possible full trim boost

Valid signal

CODES 51 AND 52 NON-LATCHING SOLENOIDS

A non-latching solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. The resistance between the two wires to a solenoid is too high or too low.
2. The resistance is too low between either of the two wires and ground.
If one of the conditions exists, the CHECK TRANS light will come on.
The CHECK TRANS light will go out when conditions 1 and 2 are eliminated.

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

Off-Highway
52

H or J solenoid

Off

Possible full trim boost

Valid signal

CODE 52 (H) SOLENOID (DP 8000) OR (J) SOLENOID (CLBT 9000)

A solenoid diagnostic code will be set in memory if one of the following conditions exists:
1. Resistance in the circuit across the solenoid is too high or too low.
2. One of the two wires going to the solenoid is in contact with an external voltage.
If one of the conditions exists, the CHECK TRANS light will come on.
The CHECK TRANS light will go out when the condition is corrected.

COPYRIGHT 1994 GENERAL MOTORS CORP.

H-23

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

DO NOT
SHIFT
Light

Description

Transmission Response

Clearing CHECK
TRANS Light

On-Highway

53

H solenoid:
On test

Off

May not shift

ECU power off/on

Off test

On

Drop LU and hold in gear

ECU power off/on

CODE 53 NEUTRAL/RANGE SOLENOIDS

There are two situations where a neutral range solenoid diagnostic code will be set in memory.
During a test when the solenoid is on, the voltage should be above a pre-set low voltage figure.
If this condition is not met, the CHECK TRANS light will come on and you may not be able to shift.
To clear the condition, the input power must be shut off and then back on.

Code

DO NOT
SHIFT
Light

Description

Transmission Response

Clearing CHECK
TRANS Light

Off-Highway

53

I solenoid:
On test

Off

May not shift

ECU power off/on

Off test

On

Drop LU and hold in gear

ECU power off/on

CODE 53 (I) SOLENOID (DP 8000)

There are two situations where a solenoid diagnostic code will be set in memory.
Resistance on the solenoid circuit is too high or the circuit is in contact with an external voltage source.
If this condition is met, the CHECK TRANS and DO NOT SHIFT lights will come on. All shifts will
be blocked.
To clear the above condition, the engine must be shut off and restarted and the condition must not be present.
Resistance on the solenoid circuit is too low
If this condition is met, the CHECK TRANS light will come on and you may not be able to shift.
To clear the above condition, the engine must be shut off and restarted and the condition must not be present.

H-24

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

DO NOT
SHIFT
Light

Description

Transmission Response

Clearing CHECK
TRANS Light

On-Highway
54

A, B, C, D, F, & J solenoids
Off test

On

Drop LU and hold in gear

ECU power off/on

CODE 54 LATCHING SOLENOID CHAIN

A latching solenoid chain diagnostic code will be set in memory if the voltage across the solenoid chain does not
equal a pre-set voltage figure.
If this condition is present, the CHECK TRANS and the DO NOT SHIFT lights will come on. Lockup will
be dropped and all shifts will be blocked.
NOTE: Lockup will be dropped unless the retarder is applied.
To clear this situation, the input power must be shut off and back on again.

Code

DO NOT
SHIFT
Light

Description

Transmission Response

Clearing CHECK
TRANS Light

Off-Highway
54

A, B, C, D, E solenoids
Off test

On

Drop LU and hold in gear

ECU power off/on

CODE 54 SOLENOID CHAIN

A solenoid diagnostic code will be set in memory if the voltage across the solenoid chain does not equal a pre-set
voltage figure.
If this condition is present, the CHECK TRANS and the DO NOT SHIFT lights will come on. Lockup will
be dropped and all shifts will be blocked.
NOTE: Lockup will be dropped unless the retarder is applied.
To clear this situation, the engine must be shut off and restarted and the condition must not be present.

COPYRIGHT 1994 GENERAL MOTORS CORP.

H-25

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

Off-Highway

61

G solenoid on test:
Below 500 output rpm

Off

May not shift

ECU power off/on

Above 500 output rpm

On

Drop LU and hold in gear

ECU power off/on

CODE 61 (G) SOLENOID

A solenoid diagnostic code will be set in memory if the voltage across the solenoid does not equal a pre-set
voltage figure.
If this condition is present, the CHECK TRANS and the DO NOT SHIFT lights will come on. Lockup will
be dropped and all shifts will be blocked.
NOTE: Lockup will be dropped unless retarder is applied.
To clear this situation, the engine must be shut off and restarted and the condition must not be present.

Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

Off-Highway
F solenoid:
Off test

On

Hold in gear

ECU power off/on

Off
On

May not shift

Hold in gear

ECU power off/on

ECU power off/on

62
On test, below 500 rpm
On test, above 500 rpm

CODE 62 (F) SOLENOID

A solenoid diagnostic code will be set in memory if one of the following conditions is met:
1. Resistance in the circuit across the solenoid is too low.
2. Internal ECU switching problem.
3. One of the two wires going to the solenoid is shortened to ground.
4. Resistance in the circuit across the solenoid is too high.
If conditions 1 and 2 are met, the CHECK TRANS light will be turned on.
If conditions 3 and 4 are met, the CHECK TRANS and DO NOT SHIFT lights will be turned on.
To clear this situation, the engine must be shut off and restarted and the condition must not be present.

H-26

COPYRIGHT 1994 GENERAL MOTORS CORP.

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION
Code

Description

DO NOT
SHIFT
Light

Transmission Response

Clearing CHECK
TRANS Light

Off-Highway
63

G solenoid on test

On

Drop LU and hold in gear

ECU power off/on

CODE 63 (G) SOLENOID

A solenoid diagnostic code will be set in memory if the voltage across the solenoid does not equal a pre-set
voltage figure.
If this condition is present, the CHECK TRANS and the DO NOT SHIFT lights will come on. Lockup will
be dropped and all shifts will be blocked.
NOTE: Lockup will be dropped unless retarder is applied.
To clear this situation, the engine must be shut off and restarted and the condition must not be present.

Code
66

Description
Transmission engine
communication link

DO NOT
SHIFT
Light
Off

Transmission Response
Fixed throttle assumed
Fixed engine rpm assumed

Clearing CHECK
TRANS Light
Next valid signal

CODE 66 TRANSMISSION ENGINE COMMUNICATION LINK (TECL)

A TECL code will be set in the absence of input signals from the DDEC ECM.
This condition will turn on the CHECK TRANS light and assume a calibrated throttle sensor setting and shift
points. This calibrated throttle sensor setting will provide shift points between closed throttle and full throttle.
When the signal is restored, the CHECK TRANS light will be turned off and normal throttle sensor readings
resumed. The Code 66 will be retained in memory until cleared.

COPYRIGHT 1994 GENERAL MOTORS CORP.

H-27

ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL

APPENDIX H DIAGNOSTIC CODE BACKGROUND INFORMATION

Code
69

Description
Electronic control unit test

DO NOT
SHIFT
Light
On

Transmission Response
Drop LU and hold in gear

Clearing CHECK
TRANS Light
ECU power off/on

CODE 69 COMPUTER MALFUNCTION

A computer malfunction diagnostic code will be set in memory if the computer locates an abnormal condition
within itself.
If an abnormal condition is found, the computer turns itself off. The CHECK TRANS and DO NOT SHIFT
lights come on and all shifts are blocked.
To clear, the input power must be shut off and back on again, and the condition must not be present.

H-28

COPYRIGHT 1994 GENERAL MOTORS CORP.