1999 MITSUBISHI LANCER EVOLUTION VI ECU

REAR AXLE – Troubleshooting 27-30
LISTING OF RESISTANCE AND CONTINUITY ACROSS CONNECTOR TERMINALS ON HARNESS
SIDE

Measure the resistance and check for continuity with the ignition switch in the “OFF” position and
AYC-ECU connector disconnected.

Measure the resistance and check for continuity across terminals listed below.

Fig. below shows the arrangement of terminals.
Terminal No.Signal nameNormally
2 – body groundLongitudinal acceleration sensor ground, lateral acceleration sensor groundConducting
26 – body groundECU groundConducting
35 – body groundAYC motor relayConducting
37 – body groundDirectional control valve (right)15.4 – 16.4 Ω
38 – body groundProportioning valve3.4 – 4.0 Ω
45 – body groundDirectional control valve (left)15.4 – 16.4 Ω
46 – body groundECU groundConducting
6 – 19*2Speed sensor (front, RH)1.4 – 1.8 kΩ
7 – 20*2Speed sensor (front, LH)1.4 – 1.8 kΩ
8 – 21*2Speed sensor (rear, RH)1.4 – 1.8 kΩ
9 – 22*2Speed sensor (rear, LH)1.4 – 1.8 kΩ
NOTE
*2: Indicates the vehicles without ABS.

REAR AXLE – On-vehicle Service 27-33
TORQUE TRANSFER MECHANISM
1. Remove the drain plug to discharge the gear oil.
2. Fit the drain plug and tighten it to the specified torque.
3. Remove the filler plug.
4. Pour the specified gear oil up to the bottom end of the
filler plug hole using an oil syringe (recommended tool)
through the gap between the body and the differential
support arm.
Specified gear oil:
MITSUBISHI GENUINE DIA QUEEN SUPER AYC
FLUID
Quantity used: 0.70
0
0.05

5. Fit the filler plug and tighten it to the specified torque.
FLUID LEVEL CHECK
1. Remove the maintenance lid located in the luggage
compartment.
2.
If the vehicle has been run, leave it for 5 min. or more
in an ordinary temperature (10C to 30C) to allow the
accumulator internal pressure to drop.
NOTE
If the ambient temperature is less than 10C or less,
allow more time to leave the vehicle to stand idle.

Connect the MUT-II to the 16-pin diagnosis connector.
Turn on the ignition switch. Operate the MUT-II (Item
No.11) to activate the hydraulic unit forcibly for removing
the pressure from inside the accumulator.
Caution
Before connecting or disconnecting the MUT-II,
always turn off the ignition switch.
NOTE
(1) The forced activation (oil level check mode) will be
automatically canceled as soon as the directional
valve in the hydraulic unit is activated to the left and
right 20 times.
It can also be canceled forcibly by operating the clear
key on the MUT-II.
(2) While this function is being disabled by the fail-safe
function, the forced activation of the hydraulic unit
can not be executed.
3. Check that the fluid level in the oil reservoir is in the
range between MAX and MIN.
4. If the fluid level is lower than MIN, add the specified
fluid.
Specified fluid: Dia Queen ATF SP II or equivalent
5. Reinstall the maintenance lid.
Gear oil
Drain plug
49 Nm
Oil syringe
(Recommended tool)
Filler plug
49 Nm

REAR AXLE – On-vehicle Service REAR AXLE – On-vehicle Service 27-34
BLEEDING
1. Lift up the vehicle.
2. Connect the MUT-II to the 16-pin diagnosis connector.
Caution
Before connecting or disconnecting the MUT-II,
always turn off the ignition switch.
3. Turn on the ignition switch.
4. Operate the MUT-II (Item No.10) to activate the hydraulic
unit forcibly.
NOTE
(1) The forced activation (air bleeding mode) will be
automatically canceled after 5 minutes operation. It
can also be canceled forcibly by operating the clear
key on the MUT-II.
(2) While this function is being disabled by the fail-safe
function, the forced activation of the hydraulic unit
can not be executed.
5. Remove the cap of the left bleeder screw on the torque
transfer differential and connect a vinyl hose.
6. Gradually turn the steering wheel clockwise from the
straight-ahead position. At this time, loosen the left bleeder
screw and check that fluid is discharged with air.
7. After air has been completely discharged, tighten the
bleeder screw.
Caution
While the system is being bled of air, add fluid as
necessary to ensure that it is left in the oil reservoir
during the entire procedure.
8. Repeat steps (6) and (7) two to three times until no air
bubbles are recognized in the fluid that comes out. Then,
tighten the bleeder screw to the specified torque.
Tightening torque: 9 Nm
9. Perform steps (5) through (8) for the right bleeder screw.
Note, however, that the steering wheel should be turned
counterclockwise.
10. After the system has been completely bled of air, check
for the fluid level. (Refer to P.27-33.)
Caution
If the system is not completely bled of air, the hydraulic
unit could generate noise, degrading pump durability.
AYC OPERATION CHECK
1. Lift up the vehicle.
2. Connect the MUT-II to the 16-pin diagnosis connector.
Caution
Before connecting or disconnecting the MUT-II, always
turn off the ignition switch.
3. Start the engine.
4. Operate the MUT-II with the transmission in 2nd or a
higher gear and check to ensure that the vehicle speed
is higher than 10 km/h using the Data List (Item 10).
Bleeder
screws Vinyl hose

REAR AXLE – On-vehicle Service 27-35
NOTE
(1) Hold the steering wheel in the neutral position.
(2) If the steering wheel is turned, it may happen that
the AYC system continues to operate (operation
sounds are heard from the torque transfer differential).
However, it does not mean a system failure. If such
a case is encountered, perform the following
operations with the steering wheel in the neutral
position to cancel the AYC function.

Disengage the clutch.

Set the transmission to neutral.

Stop the engine.
5. Operate the MUT-II (Item Nos.13 and 14) to activate
the torque transfer differential.
NOTE
(1) The forced activation (clutch operation mode) will be
automatically canceled after 1 minute operation.
It can also be canceled forcibly by operating the clear
key on the MUT-II.
(2) While this function is being disabled by the fail-safe
function, the forced activation of the torque transfer
differential can not be executed.
6. Operate the MUT-II to confirm that the several speeds
of the wheels are as shown below, using the Data List
(Item Nos.07 and 08).

The speed of left rear wheel is more than 2 km/h
higher than that of right rear wheel.

The speed of right rear wheel is more than 2 km/h
higher than that of left rear wheel.
NOTE
If the above requirements are not satisfied, the system
is probably failed. Check the hydraulic pressure.
HYDRAULIC PRESSURE CHECK
1. Lift up the vehicle.
2. Connect the MUT-II to the 16-pin diagnosis connector.
Caution
Before connecting or disconnecting the MUT-II,
always turn off the ignition switch.
3. Turn on the ignition switch.
4. Disconnect the joint between the hydraulic unit and the
hydraulic unit hose assembly. Connect the special tool
to the L port. To the R port, attach a blind plug or connect
the L port of the removed hydraulic unit hose assembly.
5. Operate the MUT-II (Item No.13) to activate the hydraulic
unit.
NOTE
(1) The forced activation (clutch left side operation check
mode) will be automatically canceled after 1 minute
operation.
It can also be canceled forcibly by operating the clear
key on the MUT-II.
MB991705
MD998330

REAR AXLE – On-vehicle Service 27-36
(2) While this function is being disabled by the fail-safe
function, the forced activation of the hydraulic unit
can not be executed.
6. Check to ensure that the hydraulic pressure generated
by the hydraulic unit conforms to the standard value.
Standard value: 1.0 – 1.6 MPa
NOTE
During checking the hydraulic pressure, occasionally
replenish the oil reservoir with fluid so that it does not
become empty.
7. Check the hydraulic pressure of the clutch right side by
repeating the steps (4) through (6). At this time, however,
the special tool must be connected to the R port and
the blind plug or the R port of the removed hydraulic
unit hose assembly must be attached to the L port. Further,
the MUT-II must be operated in the forced activation mode
Item No. 14 (clutch right side operation check mode).
8. If the measured value exceeds the standard value, replace
the hydraulic unit.
9. Connect the hydraulic unit hose assembly to the hydraulic
unit and to the torque transfer differential and tighten
the flare nuts to the specified torque.
Specified torque: 34 Nm
10. Pour the specified fluid in the oil reservoir up to the MAX
mark. Then, bleed the system.
Specified fluid: Dia Queen ATF SP II or equivalent
Fluid amount used: Approx. 1

DIFFERENTIAL CARRIER OIL SEAL
REPLACEMENT
DIFFERENTIAL
1. Remove the drive shaft.
2. Remove the oil seal from the differential carrier.
3. Using the special tool, drive a new oil seal all the way
into position.
4. Coat the oil seal lips and the drive shaft surface in contact
with the oil seal with multi-purpose grease.
5. Replace the drive shaft circlip with a new one and mount
the drive shaft to the differential carrier.
6. Check for correct wheel alignment.
TORQUE TRANSFER MECHANISM
1. Remove the drive shaft.
2. Remove the oil seal from the differential carrier.
3. Using the special tool, drive a new oil seal all the way
into position.
4. Coat the oil seal lips and the drive shaft surface in contact
with the oil seal with the specified grease.
Specified grease: Vaseline
5. Replace the drive shaft circlip with a new one and mount
the drive shaft to the differential carrier.
6. Check for correct wheel alignment.
MB990938
MB991115
MD998829
MD998812
MD998813

REAR AXLE – On-vehicle Service 27-37
WHEEL SPEED SENSOR OUTPUT VOLTAGE
MEASUREMENT
1. Lift up the vehicle and release the parking brake.
2. Disconnect the AYC-ECU harness connector and take
measurements on the harness side connector.
Caution
Insert the probe from the harness side with the double
lock of the connector unlocked. Inserting it to the
terminal side could result in poor contact.
3. Turn the wheel to be tested at about 1/2 to one
revolution/sec. and check for the output voltage using
a circuit tester (AC mV range) or oscilloscope.
Terminal nos.
Front LHFront RHRear LHRear RH
7698
20192221
Output voltage:
When circuit tester is used: 70 mV or more
When oscilloscope is used: 200 mVp-p or more
(4) If the output voltage is lower than the above value, it
is probably attributable to the following faults. Check or
replace the wheel speed sensor as necessary.

Excessive clearance between the pole piece and rotor
of the wheel speed sensor

Defective wheel speed sensor
Waveform Check Using Oscilloscope
Check the harness and connector of the wheel speed sensor
for connection. Then, use an oscilloscope to check for output
voltage waveform of each sensor as follows.
Start the engine and monitor the sensor by turning the wheel;
for a driving wheel, let it turn by shifting into the 1st gear
and for a driven wheel turn it manually at a constant speed.
NOTE
(1) Waveform may be observed by actually running the
vehicle.
(2) The output voltage is low when the wheel speed remains
low and builds up as the wheel speed increases.
AYC-ECU connector harness side
When turned manually
At idle (5 to 6 km/h)
1st gear

REAR AXLE – On-vehicle Service 27-38
Waveform Observation Points
SymptomProbable causeAction
Waveform amplitude is too small, or no
waveform.Defective wheel speed sensorReplace sensor.
Waveform amplitude varies greatly. (No
problem ifthe smallest amplitude is 100
Excessive axle hub lateral and radial runoutReplace hub.
problem if the smallest amplitude is 100
mV or more)Poor AYC-ECU groundingRepair.
Noise on waveform or disturbed
waveform
Open-circuited sensorReplace sensor.
waveform
Open-circuited harnessRepair harness.
Improperly mounted wheel speed sensorCorrect sensor installation.
Missing or collapsed ABS rotor toothReplace ABS rotor.
Caution
Since the wheel speed sensor cable follows the movement of the front or rear suspension, it
may be open-circuited only when the vehicle is run on rough roads and not on ordinary road.
The wheel speed sensor output voltage waveform should therefore be checked also by rocking
the sensor harness so that driving on rough roads may be simulated.
ACTION WHEN BATTERY RUNS OUT
When the engine is started using a booster cable where the
battery has completely run down and you attempt to start
the vehicle without waiting for the battery to recover a certain
charge, the engine can misfire and you just cannot start to
move it. In such cases, charge the battery sufficiently; or,
remove the AYC fusible link from the engine compartment
relay box to make AYC inactive before attempting to start
the vehicle. When the fusible link is removed, the AYC warning
lamp lights up. After the battery has been recharged, fit the
fusible link back again and start the engine to ensure that
the AYC warning lamp is off.AYC fusible link

REAR AXLE – Sensor Relay / AYC-ECU27-42
INSPECTION
1. LONGITUDINAL AND LATERAL ACCELERATION
SENSOR CHECK
Refer to GROUP 35B – Acceleration Sensor.
2. AYC RELAY CONTINUITY CHECK
Battery voltageTerminal No.
1345
When not energized
When energized
AYC-ECU
REMOVAL AND INSTALLATION
Pre-removal and Post-installation Operation

Front Floor Console Removal and Installation
5 Nm
AYC-ECU
5 Nm