2-1

POWER TRAIN
CONTENTS

CLUTCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 AYC SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Active Yaw Moment Control . . . . . . . . . . . . . 12
MANUAL TRANSMISSION . . . . . . . . . . . . . . . 3
Purpose of Active Yaw Moment Control . . . . 12
Transmission Control . . . . . . . . . . . . . . . . . . . . . . . 3 Cornering Model
with Yaw Moment Added . . . . . . . . . . . . . . . . . 12
PROPELLER SHAFTS . . . . . . . . . . . . . . . . . . . 4 Yaw Moment Creation Method . . . . . . . . . . . . 12
Structure And Operation . . . . . . . . . . . . . . . . 13
FRONT AXLE . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
System Configuration . . . . . . . . . . . . . . . . . . . . . 13
Drive Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Torque Transfer Differential . . . . . . . . . . . . . . . 14
Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
REAR AXLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Hydraulic Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Drive Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
AYC-ECU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Differential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2-2 POWER TRAIN – Clutch

CLUTCH
<EVOLUTION-IV>
A clutch with a pull-type diaphragm spring is utilized to enhance the disengagement characteristics and
lighten the pedal action during high-speed operation.
Specifications

Drive system 4WD

Engine 4G63 DOHC-T/C
Control system Hydraulic
Clutch disc type Dry; single
Clutch disc size (mm) 230  150
Clutch cover type Diaphragm spring (pull-type)
Clutch cover load setting (N {kgf}) 7,845 {800}
Release cylinder size (mm) 20.6
Flexible flywheel No

<EVOLUTION-V>
The EVOLUTION-V’s clutch is basically the same as the EVOLUTION-IV’s clutch. In light of the engine’s
higher torque, however, the clutch cover set load has been increased.
Specifications

Item EVOLUTION-IV EVOLUTION-V

Clutch cover load setting (N {kgf}) 7,845 {800} 8,826 {900}
 POWER TRAIN – Manual Transmission 2-3
MANUAL TRANSMISSION
The W5M51 transmission has been newly adopted.
Specifications

Model W5M51 (Normal type) W5M51 (With super cross gear)

Engine 4G63 DOHC-T/C
Type Forward 5-speed, constant mesh
Reverse One-speed, constant mesh
Gear ratios 1st 2.785 (39/14)
(numbers of teeth)
2nd 1.960 (39/20)
3rd 1.407 (38/27) 1.444 (39/27)
4th 1.031 (33/32) 1.096 (34/31)
5th 0.761 (32/42) 0.825 (33/40)
Reverse 3.416 (41/12)
Final reduction ratio (numbers of teeth) 4.529 (77/17) 4.875 (78/16) or 4.529 (77/17)
Transfer Reduction ratio 1/3.312 (16/53)
(numbers of teeth)
Limited-slip differential VCU
Reverse synchromesh Yes
Speedometer gear ratio 29/36 30/36 29/36 30/36
Front limited-slip differential Helical-gear type

TRANSMISSION CONTROL
The transmission control mechanism is basically the same as that of the previous model. However, the
gear shift lever has a shorter stroke.
2-4 POWER TRAIN – Propeller Shafts

PROPELLER SHAFTS
<EVOLUTION-IV>
The propeller shafts are basically the same as those of EVOLUTION-III. However, the specifications of
the rear propeller shaft have been revised as shown below.
Specifications

Item RS GSR EVOLUTION-III

Type Three-joint; multi-part
Length  diameter mm Front 676.5  65
Center 505  65
Rear 666.5  65 (684.5  65) 684.5  65 666.5  65

NOTE:
(1) The length of each propeller shaft is given as the distance between the centers of the joints.
(2) Figures in parentheses apply to vehicles fitted with the AYC system.
<EVOLUTION-V RS>
The joint between the rear propeller shaft and the rear differential has been changed from a Löbro joint
(LJ) to a Cardan universal joint.

Rear propeller <New>

Center propeller shaft
shaft
Front propeller
shaft

Center bearing <Old>

 POWER TRAIN – Front Axle 2-5
FRONT AXLE
To match the high-performance engine, the front axle has been revised as follows:
D Unit ball bearings are used for the wheel bearings to enhance rigidity.
D For easier maintenance, the wheel bearings are bolted onto the knuckles.
D In light of the engine’s higher output, the number of hub bolts has been increased from four to five.
Configuration

Output shaft

Knuckle

Wheel bearing Knuckle

Front hub

Front hub

Wheel bearing

<EVOLUTION-V>
DRIVE SHAFTS
In accordance with the wider tread, the joint-to-joint distances (see dimension “A” in the drawing) have
been increased as shown in the following table.

Item EVOLUTION-IV EVOLUTION-V

Joint-to-joint distance (mm) Right-hand 418 442
side
Left-hand 348 365
side
2-6 POWER TRAIN – Rear Axle

REAR AXLE
To match the high-performance engine, the rear axle has been revised as follows:
D For easier maintenance, the wheel bearings are bolted onto the knuckles.
D In light of the engine’s higher output, the number of hub bolts has been increased from four to five.
D On ABS-equipped vehicles, wheel speed sensor rotors are fitted on the drive shafts and wheel speed
sensors are fitted on the knuckles.
Configuration

Knuckle

Rear hub

Rear hub

Drive shaft Drive shaft

Rotor (ABS-equipped
vehicles only)

Wheel bearing

<EVOLUTION-V>
DRIVE SHAFTS
(1) In accordance with the wider tread, the joint-to-joint distances (see dimension “A” in the drawing)
have been increased as shown in the following table.

EVOLUTION-IV EVOLUTION-V
Item Without AYC With AYC Without AYC With AYC
system system system system
Joint-to-joint distance (mm) Right-hand 560 435 578 453
side
Left-hand 480 425 498 443
side
(2) On the GSR model, the joints closer to the differential have been changed from the double-offset
type (DOJ) to the tripod type (TJ). (On the RS model, tripod joints were already used.)

(changed from DOJ

on GSR model)
 POWER TRAIN – Rear Axle 2-7
DIFFERENTIAL
Vehicles without the AYC system are fitted with a mechanical LSD. The LSD is basically the same as
that of the EVOLUTION-III.
NOTE
For details of the LSD fitted on vehicles with the AYC system, refer to page 2-14.
Specifications

Item Mechanical LSD

Reduction gear type Hypoid gears
Reduction ratio 3.312
Differential gear (type  quantity) Side gear Straight bevel gear  2
Pinion gear Straight bevel gear  4
Number of teeth Drive gear 53
Drive pinion 16
Side gear 16
Pinion gear 10
Bearing (outside diameter  inside di- Side 72  35
ameter) (mm)
Front 62  25
Rear 72  35

<EVOLUTION-IV>

Insulator
Differential
support member

Differential
support arm
2-8 POWER TRAIN – Rear Axle

<EVOLUTION-V RS>
D The differential’s reduction gear ratio has been revised from 3.312 to 3.307.
D The differential support member is joined to the body without insulators, yielding a stiff joint that enhances
the body’s torsional rigidity. Also, the differential support member is made from cast aluminum for
lightness.
<EVOLUTION-V>

Toe control bar

Differential support member

(cast aluminum)

Differential
support arm

Differential mounting
bracket

Insulator
 POWER TRAIN – AYC System 2-9
AYC SYSTEM
The active yaw control (AYC) system is available with the EVOLUTION-IV <standard on GSR; optional
on RS>. The system actively controls the difference in driving force between the left and right rear wheels,
thereby adjusting the vehicle’s yaw moment such that all four tires perform to their maximum potential.
As a result, safety is enhanced for all drivers.
[World-Leading Technology]
The AYC system incorporates a torque transfer differential. Newly developed by Mitsubishi Motors, this
device allows torque to be transferred between the left and right wheels as required.
[Maximized Safety]
(1) Even when the vehicle is driven near the edge of its performance envelope, the AYC system ensures
that it responds faithfully and naturally to the driver’s steering and accelerator inputs. Thus, controllability
is optimized at all times.
(2) By suppressing sudden changes in vehicle behavior during acceleration and deceleration, the AYC
system provides superior stability.
System Configuration

Lateral G sensor Reservoir tank

AYC warning
lamp Steering wheel sensor

Longitudinal
G sensor
Throttle position
sensor

Hydraulic unit
Wheel speed sensor
Torque transfer
ABS-ECU differential
AYC-ECU
2-10 POWER TRAIN – AYC System

Major Components

Reference
Component Function
page
AYC-ECU Calculates direction and magnitude of required torque transfers in 2-20
accordance with data from sensors and switches, and controls hy-
draulic unit accordingly
Controls diagnosis and fail-safe functions 2-22
ABS-ECU Monitors ABS operating status —
Throttle position sensor Informs AYC-ECU when engine is idling 2-16
Provides AYC-ECU with data on throttle valve opening
AYC warning lamp Illuminates in event of system failure (also illuminates for 1.5 se- 2-22
conds when ignition switch is turned to ON position)
Stop lamp switch Provides AYC-ECU with data to enable evaluation of brake operat- —
ing status
Longitudinal G sensor Provides AYC-ECU with data on vehicle’s rate of longitudinal ac- 2-16
celeration
Lateral G sensor Provides AYC-ECU with data on vehicle’s rate of lateral accelera- 2-16
tion
Steering wheel sensor Provides AYC-ECU with data on steering wheel angle 2-16
Informs AYC-ECU when steering wheel is in straight-ahead posi-
tion
Wheel speed sensor Provides AYC-ECU with data on wheel speed 2-16
(one on each wheel)
Hydraulic Hydraulic switch Provides AYC-ECU with data on accumulator pressure 2-17
unit
Electric pump Produces hydraulic pressure for clutch actuation
Direction control Determines whether hydraulic pressure is supplied to left-hand
valve clutch or right-hand clutch
Proportioning valve Controls supply of hydraulic pressure to clutches
Electric pump relay Supplies power to electric pump —
Torque transfer differential Apportions torque to driven wheels 2-14
 POWER TRAIN – AYC System 2-11
AYC System Configuration

<Fitted in ABS-equipped vehicles>

ABS monitor signals

Wheel speed sensor (FL)
ABS- Wheel speed sensor (RL) AYC warning lamp
ECU
Wheel speed sensor (RR)
Wheel speed sensor (FR)
Diagnosis
connector

Wheel speed sensor (FL)*

Wheel speed sensor (RL)* Direction control valve
AYC-ECU
Wheel speed sensor (RR)*
Wheel speed sensor (FR)* Proportioning valve
Longitudinal G sensor
Lateral G sensor
Stop lamp switch
Steering wheel sensor Electric pump relay
Hydraulic switch
Throttle position sensor
ECU power supply

Electric pump relay

Steering wheel (in engine
sensor compartment)
Reservoir
tank
Hydraulic
Stop lamp switch switch
Front-right wheel Rear-right wheel

Accu-
mulator
Wheel speed Wheel speed Direction
sensor (FR) sensor (RR) Propor- control
valve
tioning
valve
Right-hand Direction
clutch
control
Left-hand
clutch valve

Lateral Hydraulic unit

G sensor
Longitudinal
G sensor Torque transfer
differential

Wheel speed Wheel speed

sensor (FL) sensor (RL)

Front-left wheel Rear-left wheel

NOTE
*: Vehicles without ABS
2-12 POWER TRAIN – AYC System

JACTIVE YAW MOMENT CONTROL

PURPOSE OF ACTIVE YAW MOMENT CONTROL
Active control of the vehicle’s yaw moment enables all four tires to perform to their maximum potential,
resulting in enhanced cornering performance and safety under a wide range of operating conditions.

CORNERING MODEL WITH YAW MOMENT ADDED

The addition of a yaw moment (created by causing a difference in driving force or braking force between
the left and right tires) causes the vehicle to turn inward. The front-wheel cornering force caused by the
steering wheel angle thus becomes smaller than that of a conventional vehicle, so cornering on any given
radius becomes possible with a smaller steering wheel angle. The loading applied to the front tires decreases,
and the loading applied to the rear tires increases accordingly.

<Conventional vehicle> <Vehicle with yaw moment added>

Direction of motion
Loading
decreased

Yaw moment
Cornering force
Loading
increased

Cornering on given radius is possible

with smaller steering wheel angle.

Input Difference in YAW MOMENT CREATION METHOD

driving force
The AYC system creates a yaw moment by using the torque
transfer differential to control the difference in driving force
between the left and right wheels.

Transfer of Torque transfer

driving force differential
 POWER TRAIN – AYC System 2-13
JSTRUCTURE AND OPERATION
SYSTEM CONFIGURATION
The AYC system’s main components are the torque transfer differential (this is a rear differential that
incorporates a torque transfer mechanism), the hydraulic unit, and the AYC-ECU that controls them. The
hydraulic unit incorporates an electric pump, a direction control valve, and a proportioning valve. It supplies
hydraulic pressure to the torque transfer differential. The AYC-ECU monitors driver inputs and road conditions
in accordance with data from various sensors and determines the optimum magnitude and direction of
torque transfers accordingly.

Engine
T/M

Sensors
Yaw moment Hydraulic unit
Wheel speed sensors

Longitudinal G sensor
Proportion-
ing valve
AYC-ECU Lateral G sensor
Direction
control valve Steering wheel sensor
Torque change Throttle position sensor

Torque transfer
Torque change

Torque transfer differential

(differential mechanism + speed increasing/decreasing gearing + two wet multi-disc clutches)
2-14 POWER TRAIN – AYC System

TORQUE TRANSFER DIFFERENTIAL

The torque transfer differential consists of a differential mechanism, speed increasing/decreasing gearing,
and two wet multi-disc clutches. The differential mechanism is lubricated by hypoid gear oil, and the speed
increasing/decreasing gearing and clutches (these constitute the torque transfer section) are lubricated
by AYC fluid.

Left-hand
clutch
Differential mechanism wet multi-disc type
Right-hand
clutch

Speed-
reducing gear
Speed- Speed increasing/
increasing gear decreasing gearing
Input gear

[Differential Mechanism]
During cornering maneuvers, the differential mechanism allows the vehicle’s inside and outside wheels
to turn at different speeds.
[Speed Increasing/Decreasing Gearing]
The speed increasing/decreasing gearing increases or decreases the speeds of the left- and right-hand
wet multi-disc clutches relative to the speed of the right wheel.
[Wet Multi-Disc Clutches]
The wet multi-disc clutches transfer torque from the faster wheel to the slower wheel. When the left-hand
clutch operates, the speed-reducing gear causes a torque transfer from the right wheel to the left wheel.
When the right-hand clutch operates, the speed-increasing gear causes a torque transfer from the left
wheel to the right wheel.
[Comparison of Torque Transfer Differential and LSD]

Device Torque transfer differential LSD

Components Differential mechanism + speed increasing/de- Differential mechanism + one wet multi-disc
creasing gearing + two wet multi-disc clutches clutch or viscous coupling unit
Function Permits transfer of torque in either direction and Transfers torque from inside wheel (during cor-
thus enables control of yaw moment. nering maneuver) or spinning wheel to wheel on
opposite side.
 POWER TRAIN – AYC System 2-15
Principle of Operation in Torque Transfer Differential
Faster side Slower side When two clutch plates with different rotational speeds are
pressed against each other, torque is transferred from the
faster disc to the slower disc. The amount of torque transferred
is proportional to the force with which the discs are pressed
Pressing Pressing together. In the torque transfer differential, these properties
force force
are utilized to allow torque to be transferred as required.
The speed increasing/reducing gearing is permanently
Torque transfer meshed. Relative to the input speed of the differential case,
Left- the left-hand clutch, which is meshed with the speed-reducing
Differential case
hand gear, turns more slowly and the right-hand clutch, which is
clutch Right-hand meshed with the speed-increasing gear, turns more quickly.
clutch
The housing of the left- and right-hand clutches is linked to
the rear-right drive shaft, so activation of the left- or right-hand
clutches permits torque to be transferred toward either side.

Speed- Speed-
increas- reducing
ing gear gear

Flow of Torque
Cornering (1) With Left-Hand Clutch Activated
direction Yaw moment
Left-hand clutch When the left-hand clutch is activated to increase the torque
applied to the left wheel, some of the torque applied to the
right wheel is directed back to the differential case and thence
Torque (in- to the left wheel. Thus, a rightward yaw moment is applied
creased) Torque (de-
creased) to the vehicle.

(2) With Right-Hand Clutch Activated

Yaw Cornering When the right-hand clutch is activated to increase the torque
moment direction Right-hand applied to the right wheel, additional torque is directed toward
clutch
the right wheel from the differential case. Thus, a leftward
yaw moment is applied to the vehicle.
Torque
Torque (in-
(de- creased)
creased)
2-16 POWER TRAIN – AYC System

SENSORS
Wheel Speed Sensors
The wheel speed sensors are the same as those used with
ABSs. On an ABS-equipped vehicle, signals from the wheel
speed sensors are transmitted to the AYC-ECU after being
processed by the ABS-ECU.

Parking brake lever

Longitudinal G Sensor
The longitudinal G sensor is the same as that used with the
Longitudinal ABSs of earlier models. On an ABS-equipped vehicle, the
G sensor
sensor is shared by the AYC system and ABS.
Lateral G Sensor
Lateral
G sensor The lateral G sensor is the same as the longitudinal G sensor.
It is mounted at 90° to the longitudinal G sensor to enable
sensing of lateral acceleration.

Steering Wheel Sensor

The steering wheel sensor senses the degree of steering wheel
rotation and detects when the steering wheel is centered.
It is incorporated into the column switch on the steering column.

Steering wheel sensor

Throttle Position Sensor

The throttle position sensor is used by the AYC system and
for engine control purposes.
 POWER TRAIN – AYC System 2-17
HYDRAULIC UNIT
The hydraulic unit consists of an accumulator section (this contains an electric pump, a hydraulic switch,
and an accumulator) and a pressure control section (this contains a proportioning valve and a direction
control valve).
In the accumulator section, the pump is activated intermittently to maintain the required level of control
pressure in the accumulator. In the pressure control section, signals from the AYC-ECU cause the proportioning
valve and direction control valve to supply pressure to the clutches in the torque transfer differential.
Hydraulic unit

Wheel speed sensors Hydraulic switch

Steering wheel sensor Electric pump relay

Electric Accu-
pump mulator
Longitudinal G sensor
AYC-ECU

Lateral G sensor
Proportion-
ing valve
Throttle position sensor
Direction
control valve
AYC warning lamp

Electronic control system

Hydraulic control system

Left Right

Clutches

Item Specification
Electric pump Trochoid type
Hydraulic fluid ATF-SPII
Proportioning valve Current control type (direct-acting, electromagnetic, proportional pressure control valve)
Direction control valve Voltage control type (spring-centered 4-port, 2-solenoid, 3-position valve)
2-18 POWER TRAIN – AYC System

[Operation]
(1) Proportioning Valve and Direction Control Valve OFF
The proportioning valve and direction control valve are both closed, so no hydraulic pressure is supplied
to the differential.

Reservoir tank Proportioning Direction control

valve (OFF) valve (OFF)

Accumulator

Hydraulic
switch

Check
valve

Electric pump Relief valve

Filter

(2) Proportioning Valve ON and Direction Control Valve OFF

The proportioning valve is opened as required to regulate the control pressure.

Reservoir tank Proportioning Direction control

valve (ON) valve (ON)
Return
Accumulator

Hydraulic
switch

Return
Check
valve

Electric pump Relief valve

Filter
 POWER TRAIN – AYC System 2-19
(3) Proportioning Valve ON and Direction Control Valve ON (L-Port Open)
Opening of the direction control valve’s L-port allows the regulated hydraulic pressure to reach the
left-hand clutch from the proportioning valve.

Reservoir tank Proportioning Direction control valve

valve (ON) (ON; L-port Open)
Return
Accumulator

Hydraulic
switch

To left-hand
Return clutch
Check L-port
valve
R-port

Electric pump Relief valve

Filter

(4) Proportioning Valve ON and Direction Control Valve ON (R-Port Open)

Opening of the direction control valve’s R-port allows the regulated hydraulic pressure to reach the
right-hand clutch from the proportioning valve.

Reservoir tank Proportioning Direction control valve

valve (ON) (ON; R-port Open)
Return
Accumulator

Hydraulic
switch

Return
Check L-port
valve
R-port
To right-hand
clutch

Electric pump Relief valve

Filter
2-20 POWER TRAIN – AYC System

Proportioning Valve
The proportioning valve adjusts the control pressure in accor-
dance with signals from the AYC-ECU.
Direction
control valve Propor- Direction Control Valve
tioning
valve The direction control valve directs the control pressure to the
left- and right-hand clutches in accordance with signals from
the AYC-ECU.

Hydraulic Switch
Hydraulic switch The hydraulic switch issues signals to the AYC-ECU in accor-
dance with the accumulator pressure. The AYC-ECU activates
the electric pump in accordance with these signals.

AYC-ECU
The AYC-ECU evaluates the driving, vehicle, and road condi-
AYC-ECU tions using signals from various sensors and controls the hy-
draulic unit accordingly. Further, the AYC-ECU has a diagnosis
function. When it identifies a fault using this function, it termi-
nates the system’s operation and illuminates the AYC warning
lamp.
 POWER TRAIN – AYC System 2-21
Benefits of Control
(1) Control During Simultaneous Acceleration and Cornering and When Steering Wheel Angle is
Increased
Understeer tends to occur when a vehicle accelerates and corners simultaneously and when its steering
wheel angle is increased. Therefore, the AYC system creates a yaw moment in the cornering direction
by transferring torque to the outside wheel. As a result, the front wheels’ cornering force load diminishes
(in other words, the front wheels’ lateral slip force decreases) such that understeer is suppressed.
The overall benefits are linear response to steering inputs with higher levels of cornering acceleration
G and accordingly enhanced controllability during cornering maneuvers.

Improvement in
cornering performance

Without control

Steering wheel angle

Without control

With control
(understeer
suppressed)

Increased range With control

of linear steering
response

Cornering acceleration G

(2) Control on Poor Road Surfaces

When the vehicle makes a standing start with its left and right wheels on surfaces with significantly
different friction (µ) levels or is driven on a rough surface, the AYC system transfers torque to the
wheel on the higher-friction side, thereby suppressing wheelspin on the lower-friction side. Effectively,
the system functions as an LSD, thus enabling smooth acceleration and enhanced running performance
on poor roads.
Low-µ surface

High-µ
surface High-µ With control
surface
Vehicle speed

Without control

With control (standing- Without control

start and acceleration
performance improved) Time
2-22 POWER TRAIN – AYC System

AYC Warning Lamp Control

The AYC warning lamp is illuminated at the following times:
(1) For approximately 1.5 seconds when the ignition switch
is turned to the ON position (to enable the user to check
whether the bulb has blown);
(2) In the event of a fault in the AYC system (the lamp stays
illuminated until the ignition switch is turned to the OFF
position).

AYC warning lamp

Diagnosis Functions
To facilitate inspection of the AYC system, the AYC-ECU has the following functions:
D Diagnosis code output
D Service data output
D Actuator test
All of these functions can be utilized using a MUT-II.
Diagnosis Codes
There are 23 diagnosis items. Diagnosis results are stored in a volatile memory. When the ignition switch
is turned to the OFF position, a backup battery ensures that the memory’s contents are retained. (The
memory’s contents are lost if the battery is disconnected.) Diagnosis codes can be read using a MUT-II
or the AYC warning lamp. (The AYC warning lamp indicates codes by flashing.)
 POWER TRAIN – AYC System 2-23
(1) Diagnosis Items

Warning lamp:
Code No. Diagnosis item f: ON Meaning
—: OFF
12 Power supply voltage — Open/short circuit or voltage drop in power-supply-volt-
(bulb power supply) age-related circuitry
21 Wheel speed sensor f Open/short circuit in circuitry related to wheel speed sen-
(front-right) sor (front-right)
22 Wheel speed sensor f Open/short circuit in circuitry related to wheel speed sen-
(front-left) sor (front-left)
23 Wheel speed sensor f Open/short circuit in circuitry related to wheel speed sen-
(rear-right) sor (rear-right)
24 Wheel speed sensor f Open/short circuit in circuitry related to wheel speed sen-
(rear-left) sor (rear-left)
25 Wheel speed sensor — Wheels of different diameters fitted
26 Wheel speed sensor f Fault in wheel speed sensor(s)
31 Steering wheel sensor f Open circuit in circuitry related to steering wheel sensor
32 Steering wheel sensor f Short circuit in circuitry related to steering wheel sensor
33 Steering wheel sensor f Steering wheel sensor stuck in H position
34 Steering wheel sensor f Short circuit in circuitry related to steering wheel sensor
41 Throttle position sen- f Open/short circuit in circuitry related to throttle position
sor sensor
51 Longitudinal G sensor f Open/short circuit in circuitry related to longitudinal G sen-
sor
52 Longitudinal G sensor f Longitudinal G sensor jammed
56 Lateral G sensor f Open/short circuit in circuitry related to lateral G sensor
61 Stop lamp switch f Open circuit in circuitry related to stop lamp switch
65 ABS f Open circuit in ABS output line; fault in ABS
71 Proportioning valve f Open/short circuit in circuitry related to proportioning valve
72 Direction control valve f Open/short circuit in circuitry related to direction control
(right) valve (right)
73 Direction control valve f Open/short circuit in circuitry related to direction conrol
(left) valve (left)
81 Electric pump relay f Open/short circuit in circuitry related to electric pump relay
82 Hydraulic switch f Open circuit in circuitry related to hydraulic pressure
switch; pressure leak; fault in electric pump; fusible link of
motor blown
83 Hydraulic switch f Open circuit in circuitry related to hydraulic pressure
switch; electric pump relay contacts fused together
2-24 POWER TRAIN – AYC System

Indication of Diagnosis Codes Using AYC Warning Lamp

Example: Indication of diagnosis code No. 24 Normal flashing

0.5 s 0.25 s
1.5 s 0.5 s
ON ON
OFF OFF
Signals Divider
Pause (2 s) Signals
time: 3 s for multi-
ple of ten for units

(2) Deletion of Diagnosis Codes from Memory

NOTE
(1) It is not possible to delete diagnosis codes using a MUT-II unless the AYC-ECU is functioning normally.
(2) The only way to check whether the memory contents have been deleted is to try displaying them
again.
(3) Commands can still be received from the MUT-II after the memory contents have been deleted. To
confirm diagnosis codes, operate the MUT-II again.
<With MUT-II>
Delete the memory contents in accordance with messages displayed on the MUT-II. For details, refer
to the MUT-II Reference Manual or Operating Instructions.
<Without MUT-II>
Delete the memory contents by disconnecting the battery for 10 seconds or longer. (The memory contents
are cleared if the supply of backup power to the AYC-ECU is interrupted for 10 seconds or longer.)
 POWER TRAIN – AYC System 2-25
Service Data Output
Service data output items are shown in the following table.
Item No. Service data item Unit
01 Wheel speed sensor (front-right) km/h (indicated in increments of 1 km/h)
02 Wheel speed sensor (front-left) km/h (indicated in increments of 1 km/h)
03 Wheel speed sensor (rear-right) km/h (indicated in increments of 1 km/h)
04 Wheel speed sensor (rear-left) km/h (indicated in increments of 1 km/h)
05 Wheel speed sensor (front-right) (0.2 km/h) km/h (indicated in increments of 0.2 km/h)
06 Wheel speed sensor (front-left) (0.2 km/h) km/h (indicated in increments of 0.2 km/h)
07 Wheel speed sensor (rear-right) (0.2 km/h) km/h (indicated in increments of 0.2 km/h)
08 Wheel speed sensor (rear-left) (0.2 km/h) km/h (indicated in increments of 0.2 km/h)
10 Vehicle speed km/h
11 Battery voltage V
15 Throttle position sensor mV
19 G sensor (longitudinal) V
20 G sensor (lateral) V
22 Steering wheel angle deg
23 Steering wheel angular velocity deg/s
45 Idle switch ON/OFF
46 Steering wheel sensor – STN terminal ON/OFF
47 Steering wheel sensor – ST1 terminal ON/OFF
48 Steering wheel sensor – ST2 terminal ON/OFF
50 Stop lamp switch ON/OFF
56 Pressure switch High/Low
59 ABS monitor ON/OFF
2-26 POWER TRAIN – AYC System

Actuator Tests
(1) An actuator test can be performed only when the following conditions are all satisfied:
D The speed indicated by each wheel speed sensor is 20 km/h or lower.
D No system fault is detected.
D The steering wheel angle is within 30° of the steering wheel’s center position.
(2) Forced activation is cancelled if any of the following conditions exists:
D The speed indicated by any wheel speed sensor is higher than 20 km/h.
D A system fault is detected.
D The forced activation time elapses.
D The MUT-II is disconnected.
D The MUT-II’s clear key is pressed.

Item Activation
Meaning Activation Remarks
No. time
10 Air bleed Current supplied to proportioning 5 min. Check that air does not emerge
valve in accordance with steering from bleeder plug on torque trans-
wheel angle; direction control fer differential.
valve activated
11 Fluid volume Direction control valve activated Until end of Check fluid level in reservoir tank
check leftward and rightward 20 times operation
12 Electric pump Electric pump activated for 5 se- Until end of Check pump operation by listen-
operation check conds operation ing to pump’s operating sound.
13 Clutch operation Direction control valve activated; 1 min. With wheels raised, check opera-
check (left-hand) maximum hydraulic pressure sup- tion from speed difference be-
plied to left-hand clutch tween rear wheels.
14 Clutch operation Direction control valve activated; 1 min. With wheels raised, check opera-
check (right-hand) maximum hydraulic pressure sup- tion from speed difference be-
plied to right-hand clutch tween rear wheels.
15 Control OFF Electric pump relay turned OFF; — During on-road operation, check
AYC system deactivated difference in behavior with AYC
system switched ON and OFF.