ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
DIAGNOSTIC TROUBLE CODES (DTC)
DTC P0561 Unrealistic Variations in Vehicle System Voltage
J1 HARNESS CONNECTOR TCM
(GRAV)
102
J1-2
104 IGNITION
J1-4
POWER
103 BATTERY
J1-3 POWER TCM
101 J1-1 GND
IGN 105
SWITCH J1-5 GND
12V/24V
BATTERY
V06215.01.00
Circuit Description
The Transmission Control Module (TCM) requires a switched ignition voltage input and a direct battery voltage
input. This switched ignition voltage signal originates from the ignition switch or an ignition relay to supply voltage to
pins 102 and 104 in the J1 connector at the TCM. Battery direct voltage is supplied to pin 103 at the J1 connector.
Conditions for Running the DTC
• The test becomes enabled when the engine has been running above 400 rpm for at least 0.5 seconds.
• The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater
than 18V and less than 32V (24V TCM).
Conditions for Setting the DTC
P0561 sets when the TCM detects a large variation in ignition voltage or battery direct voltage. When an ignition or
battery direct voltage variation of 4.0V or greater is detected for 0.5 seconds, a fault pending is reported. After
1.0 second of 4.0V or greater variation, a OTC is set with a failure response.
Action Taken When the DTC Sets
When OTC P0561 is active, the following conditions will occur:
• OTC P0561 is stored in the TCM history.
• Hydraulic default is commanded. Shift selector position and hydraulic state of logic valves determine the range
attained.
• The CHECK TRANS light illuminates.
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ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
DIAGNOSTIC TROUBLE CODES (DTC)
• The TCM inhibits TCC engagement.
• The TCM freezes shift adapts (DNA).
Conditions for Clearing the DTC/CHECKTRANS Light
A Scan Tool may be used to clear the code from the TCM history. The TCM automatically clears the OTC from the
TCM history if the vehicle completes 40 warm-up cycles without the OTC recurring.
Diagnostic Aids
• You may have to drive the vehicle in order to experience a fault.
• This OTC indicates a variation in ignition voltage or battery direct voltage. Common ignition circuit problems for
this OTC are a fault in the feed wires to the TCM, a defective ignition switch, or a large vehicle accessory load
on the ignition circuit. Battery direct voltage problems may be due to loose or corroded battery cables, a bad
connection at the battery direct feed terminal (103), or an internal TCM failure due to a burnt trace.
• A vehicle charging system failure may cause this OTC under certain circumstances.
• This code may indicate that an internal voltage problem has occurred inside the TCM. The use of a substitute
TCM would be a good way to diagnose this problem.
• A defective vehicle battery may induce this OTC.
• Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
A bent terminal.
A backed-out terminal.
A damaged terminal.
Poor terminal tension.
A chafed wire.
A broken wire inside the insulation.
• When diagnosing for an intermittent short or open, massage the wiring harness while watching the test
equipment for a change.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This step tests for an active OTC after clearing.
3. This step tests for the proper battery direct input voltage.
4. This step tests for the proper ignition input voltage.
5. This step tests for shorts or open conditions at battery direct input circuit.
6. This step tests for shorts or open conditions at ignition input circuit.
DTC P0561 Unrealistic Variations in Vehicle System Voltage
Step Action Value(s) Yes No
1 Was the Beginning The Troubleshooting Go to Step 2 Go to
Process (Paragraph 5-4A) performed? Beginning The
Troubleshooting
Process
(Paragraph 5-4A)
5-28 Copyright© 2004 General Motors Corp.
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
DIAGNOSTIC TROUBLE CODES (DTC)
DTC P0561 Unrealistic Variations in Vehicle System Voltage
Step Action Value(s) Yes No
2 1. Install the Scan Tool. - Go to Step 3 Go to Step 4
2. Turn ON the ignition, with the engine OFF.
3. Record the failure records.
4. Clear the DTC.
5. Start vehicle and test drive.
6. Duplicate same operating conditions
observed in failure records.
NOTE: This DTC indicates that a voltage
variation exists in the ignition voltage or at
the battery direct input. This variation is
measured from min. and max. voltage
values. If the voltage variation is present for
a pre-determined amount of time, this DTC
sets.
Did DTC P0561 return?
3 1. Turn the ignition OFF. 11.5-12.5V Go to Step 4 Go to Step 5
2. Disconnect TCM connector J1 (gray) at the
TCM.
3. Install J 39700 Breakout Box and J 43799
Adapter box at the J1 connector.
4, Using a digital multimeter (DVOM), measure
voltage at J1 connector pin 1 and pin 3.
Is the voltage within the specified value?
4 1. Using a digital multimeter (DVOM), 11.5-12.5V Go to Diagnostic Go to Step 6
sequentially measure voltage at J1 Aids
connector pins 2 and 4 using J1 connector
pins 1 or 5 as ground return.
2. Turn ON the ignition, with the engine OFF.
Is the voltage within the specified value?
5 NOTE: The vehicle OEM has responsibility - Go to Step 8 Go to Step 7
for all external wiring harness repair.
Harness repairs performed by Allison
Transmission distributors and dealers are
not covered by Allison Transmission
warranty.
Inspect battery direct circuit 103 for one of the
following conditions:
• Intermittent open or short.
• Loose or corroded connections at battery
or connection points.
• Defective battery.
Was one of these conditions discovered and
repaired?
Copyright© 2004 General Motors Corp. 5-29
ALLISON 1000 AND 2000 PRODUCT FAMILIES ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
DIAGNOSTIC TROUBLE CODES (DTC)
DTC P0561 Unrealistic Variations in Vehicle System Voltage
Step Action Value(s) Yes No
6 NOTE: The vehicle OEM has responsibility - Go to Step 8 Go to Step 7
for all external wiring harness repair.
Harness repairs performed by Allison
Transmission distributors and dealers are
not covered by Allison Transmission
warranty.
Inspect the TCM ignition input circuit for one of
the following conditions:
• Intermittent open or short at ignition input
circuits 101, 102, 103, or 104.
• Loose or corroded connections at ignition
switch or ignition relay assembly.
• Defective ignition switch or relay.
• Loading of ignition circuit by defective
vehicle accessories.
Was one of these conditions discovered and
repaired?
7 NOTE: In most cases, the TCM is not at fault. - Go to Step 8 -
Investigate thoroughly before replacing the
TCM. Refer to TCM Replacement Procedure
(Section 3-6).
Replace the TCM.
Is the replacement complete?
8 In order to verify your repair: - Begin the System OK
1 . Clear the DTC. diagnosis again.
2. Drive the vehicle under conditions shown in Go to Step 1
failure records.
Did the OTC return?
5-30 Copyright© 2004 General Motors Corp.
