MITSUBISHI LANCER EVOLUTION VI 1999 Workshop Manual

REAR AXLE – Troubleshooting <AYC>27-15
Code No. 72: Directional control valve (right) systemProbable cause
This code is output when the directional control valve (right) control circuit is open-
or short-circuited.
Defective directional control valve (right)

Defective harness or connector

Defective AYC-ECU
OK
Check and repair the harness between
directional control valve (right) and
body ground.
OK
Check the trouble symptom.
OK
Replace AYC-ECU.
NG
Check the harness between directional
control valve (right) and AYC-ECU.NG
Repair
OK
Check the trouble symptom.
OK
Check the following connectors:
B-96, B-94, D-06, F-30, F-29NG
Repair
OK
Measure at F-29 directional control
valve (right) connector.

Disconnect the connector and
measure at the directional control
valve side.

Continuity across 1 and body
ground
OK:ConductingNGCheck the following connectors:
F-29, F-30NG
Repair
Measure at F-29 directional control
valve (right) connector.

Disconnect the connector and
measure at the directional control
valve side.

Resistance across 1 – 2
OK:19 – 21 Ω or lessNGReplace the hydraulic unit.

REAR AXLE – Troubleshooting <AYC>27-16
Code No. 73: Directional control valve (left) systemProbable cause
This code is output when the directional control valve (left) control circuit is open-
or short-circuited.
Defective directional control valve (left)

Defective harness or connector

Defective AYC-ECU
NG
Check and repair the harness between
directional control valve (left) and body
ground.
OK
Check the trouble symptom.
OK
Replace AYC-ECU.
NG
Check the harness between directional
control valve (left) and AYC-ECU.NG
Repair
OK
Check the trouble symptom.
OK
Check the following connectors:
B-96, B-94, D-06, F-30, F-28NG
Repair
OK
Measure at F-28 directional control
valve (left) connector.

Disconnect the connector and
measure at the directional control
valve side.

Continuity across 1 and body
ground
OK:ConductingNGCheck the following connectors:
F-28, F-30NG
Repair
Measure at F-28 directional control
valve (left) connector.

Disconnect the connector and
measure at the directional control
valve side.

Resistance across 1 – 2
OK:19 – 21 Ω or lessNGReplace the hydraulic unit.

REAR AXLE – Troubleshooting <AYC>27-17
Code No. 81: AYC relay systemProbable cause
This code is output when the coil circuit of the AYC relay is open- or short-circuited.
Defective AYC relay

Defective harness or connector

Defective AYC-ECU
NG
Check and repair the harness between
AYC relay and body ground.
OK
Check the trouble symptom.
OK
Replace AYC-ECU.
NG
Check the harness between AYC relay
and AYC-ECU.NG
Repair
NG
Check the trouble symptom.
OK
Check the following connectors:
B-96, B-126NG
Repair
OK
Measure at A-126 AYC relay connec-
tor.

Disconnect the connector and
measure at the harness side.

Continuity across 1 and body
ground
OK:ConductingNGCheck the following connector:
A-126NG
Repair
Check the AYC relay.
(Refer to P.27-42.)NGReplace the AYC relay.

REAR AXLE – Troubleshooting <AYC>27-18
Code No. 82: Electric pump systemProbable cause
This code is output if the pressure switch is not set to high-pressure position despite
the AYC-ECU’s command to drive the AYC relay for a given period of time.
Low hydraulic oil level

Oil leak

Defective fusible link

Defective AYC relay

Defective harness or connector

Defective AYC motor

Defective accumulator pressure switch

Defective AYC-ECU
OK
Replace AYC-ECU.
Check the harness
between AYC relay and
AYC motor, and between
AYC motor and body
ground.NG
Replace
NG
OK
Check the trouble symptom.
OK
Check the following
connectors:
A-126, B-94, B-27, F-32NG
Repair
OK
Replace AYC-ECU.
NG
Check the harness
between AYC-ECU and
accumulator pressure
switch.NG
Repair
NG
Check and repair the har-
ness between fusible link
no. 10 and AYC relay.
OK
Check the trouble symp-
tom.
OK
Replace the hydraulic unit
for a defective accumula-
tor pressure switch.
NO
Repair the leak.
OK
Check the trouble symptom.
NG
Check the following
connector: A-126NG
Repair
YES
Add hydraulic oil.
Is the hydraulic oil level correct in the reservoir tank?
(Refer to P.27-33.)NOIs there a hydraulic oil leak?
Measure at A-126 AYC relay connector.

Disconnect the connector and measure at the harness side.

Voltage across 5 and body ground
OK: System voltage
NG
NO
MUT-II Actuator test:
No. 12 Electric pump operation check
OK: Pump operation sounds are heardOKMeasure at F-31 accumulator pressure switch connector.

Disconnect the connector and measure at the harness side.

Ignition switch: ON

Voltage across 2 and body ground
OK:System voltage
YES
Is diagnosis code no. 81 output?YESCheck the AYC relay system. (Refer to P.27-17.)
NG
Check the following
connectors: B-95, B-94,
D-06, F-30, F-31NG
Repair
OK

Check AYC relay for
continuity.
(Refer to P.27-42.)

Check AYC motor for
operation.NG
Repair

REAR AXLE – Troubleshooting <AYC>27-19
Code No. 83: Electric pump systemProbable cause
This code is output if the pressure switch is not set to low-pressure position despite
the AYC-ECU’s command to change the driving force.
Defective accumulator pressure switch

Defective harness or connector
OK
Replace AYC-ECU.
NG
Check the harness between AYC-ECU
and accumulator pressure switch.NG
Repair
OK
Check the trouble symptom.
NG
Check and repair the harness between
accumulator pressure switch and body
ground.
OK
Check the trouble symptom.
(2) NG
Check the following connectors:
F-31, F-30NG
Repair
NO
Measure at F-31 accumulator pressure
switch connector.

Disconnect the connector and
measure at the harness side.

Ignition switch: ON
(1) Voltage across 2 and body ground
OK:System voltage
(2) Continuity across 1 and body
ground
OK:ConductingOKReplace the hydraulic unit for a defec-
tive accumulator pressure switch.
OK
Check and repair the harness between
AYC relay and AYC motor.
NO
Is diagnosis code no. 71, 72, or 73
output?YES
Check the proportioning valve
system (code no. 71).
(Refer to P.27-14.)

Check the directional control valve
(right) system (code no. 72).
(Refer to P.27-15.)

Check the directional control valve
(left) system (code no. 73).
(Refer to P.27-16.)
(1) NGCheck the following connectors:
B-95, B-94, D-06, F-30, F-31NG
Repair
Does the AYC motor continue turning
when the ignition switch is turned ON?YESCheck the AYC relay for continuity.
(Refer to P.27-42.)NG
Repair

REAR AXLE – Troubleshooting <AYC>27-20
5. INSPECTION CHART FOR TROUBLE SYMPTOMS
Trouble symptomInspection
procedure No.Ref. page
Communication between MUT-II and the whole system is not possible.127-20
Communicatio between MUT-II and AYC-ECU is not possible.227-21
AYC warning lamp does not light up when the ignition key is turned to “ON” (engine
stationary).327-22
AYC warning lamp remains lit up after the engine has started.427-23
AYC is inoperative.
Unable to start or accelerate on slippery road surfaces.527-23
Rear tires are noisy during low-speed cornering.
Vehicle skews.627-24
6. INSPECTION PROCEDURE FOR TROUBLE SYMPTOMS
INSPECTION PROCEDURE 1
Communication between MUT-II and the whole system is
not possible.
Probable cause
The cause may be a malfunction of the power supply circuit or the ground circuit
of the diagnosis connector.
Defective diagnosis connector

Defective harness or connector
NG
Check and repair the harness between
power supply and diagnosis connector.
OK
Check the trouble symptom.
NG
Check and repair the harness between
body ground and diagnosis connector.
OK
Check the trouble symptom.
OK
Replace MUT-II.
Check the following connectors:
B-22, B-50NG
Repair
OK
Measure at B-22 diagnosis connector.

Disconnect the connector and
measure at the harness side.

Continuity across 4/5 and body
ground
OK:ConductingNG
Measure at B-22 diagnosis combina-
tion meter connector.

Voltage across 16 and body ground
OK:System voltageNGCheck the following connectors:
B-22, B-49, B-75, B-73NG
Repair

REAR AXLE – Troubleshooting <AYC>27-21
INSPECTION PROCEDURE 2
Communication between MUT-II and the AYC-ECU is not
possible.
Probable cause
The cause may be a malfunction of the AYC-ECU power supply circuit or an open
circuit in the diagnosis output circuit.
Blown fuse

Defective harness or connector

Defective AYC-ECU
NG
Check and repair the harness between
AYC-ECU and diagnosis connctor.
OK
Check the trouble symptom.
OK
Check the following symptom.
NG
Check and repair the harness between
ignition switch (IG
2) and AYC-ECU.
OK
Check the trouble symptom.
OK
Replace AYC-ECU.
Check the following connectors:
B-96, B-94, B-49, B-75, B-76NG
Repair
OK
Measure at B-96 AYC-ECU connector.

Disconnect the connector and
measure at the harness side.

Ignition switch: ON

Voltage across 31 and body ground
OK:System voltageNG
Measure at B-22 diagnosis connector
and B-95 AYC-ECU connector.

Disconnect the connectors and
measure at the harness side.

Continuity across 1 of B-22 and
10 of B-95

Continuity across 7 of B-22 and
23 of B-95
OK:ConductingNGCheck the following connectors:
B-95, B-65, B-22NG
Repair
OK
Measure at B-95 and B-96 AYC-ECU
connectors.

Disconnect the connectors and
measure at the harness side.

Continuity across 26/46 and body
ground
OK:ConductingNGCheck the following connectors:
B-95, B-96NG
Replace
Check and repair the harness between
AYC-ECU and earth.
NG

REAR AXLE – Troubleshooting <AYC>27-22
INSPECTION PROCEDURE 3
AYC warning lamp does not light up when the ignition key
is turned to “ON” (engine stationary).
Probable cause
The lamp power supply circuit is probably open-circuited, lamp bulb is out, or the
circuit between AYC warning lamp and AYC-ECU or AYC-ECU itself is defective.
Blown fuse

AYC warning lamp out

Defective harness or connector

Defective AYC-ECU
NG
Check and repair the harness between
ignition switch (IG
2) and AYC warning
lamp.
OK
Check the trouble symptom.
OK
Replace combination meter.
NG
Check the harness between AYC
warning lamp and AYC-ECU.NG
Repair
OK
Check the trouble symptom.OK
Replace AYC-ECU.
OK
Check the following connectors:
B-96, B-94, B-08NG
Repair
OK
Measure at B-96 AYC-ECU connector.

Disconnect the connector and
measure at the harness side.

Ignition switch: ON

Warning lamp when 36 is grounded
to body
OK:Lit upNGCheck the lamp bulb.NG
Replace
Measure at B-08 combination meter
connector.

Disconnect the connector and
measure at the harness side.

Ignition switch: ON

Voltage across 48 and body ground
OK:Symptom voltageNGCheck the following connectors:
B-08, B-74, B-76NG
Repair

REAR AXLE – Troubleshooting <AYC>27-23
INSPECTION PROCEDURE 4
AYC warning lamp remains lit up after the engine has
started.
Probable cause
The AYC warning lamp ON circuit is probably short-circuited.
Defective combination meter

Defective harness (short-circuit)

Defective AYC-ECU
NOTE
This symptom is limited only when the communication with MUT-II is possible with AYC-ECU power supply
in normal condition and the diagnosis code is correct.
OK
Replace combination meter.
NO
Check the harness between AYC
warning lamp and AYC-ECU.NG
Repair
Does the AYC warning lamp goes out
when the B-96 AYC-ECU connector
is disconnected?YESReplace AYC-ECU.
INSPECTION PROCEDURE 5
AYC is inoperative.
Unable to start or accelerate on slippery road surfaces.
Probable cause
The hydraulic oil level is probably low, there is an oil leak, the hydraulic unit is defective,
or the torque transfer differential is defective.
Low hydraulic oil level

Oil leak

Defective hydraulic unit

Defective torque transfer differential
NOTE
This symptom is limited only when the diagnosis code is correct.
NG
Replace the hydraulic unit.
NG
Replace the torque transfer differential.
Check the trouble symptom.
NG
Replace AYC fluid.
OK
Correct
Check the trouble symptom.NO
Replace the torque transfer differential.
OK
Is foreign matter trapped in the hydrau-
lic line?YES
Repair
OK
Check the AYC for operation.
(Refer to P.27-34.)OKCheck the AYC fluid.
NG
Add hydraulic oil.
NG
Check hydraulic pressure..
(Refer to P.27-35.)NGBleed the system of air.
(Refer to P.27-34.)
Check the hydraulic oil level.NGCheck for oil leak.OK
Repair

REAR AXLE – Troubleshooting <AYC>27-24
INSPECTION PROCEDURE 6
Rear tires are noisy during low-speed cornering.
Vehicle skews.
Probable cause
The hydraulic unit or torque transfer differential is probably defective.
Defective hydraulic unit

Defective torque transfer differential
NOTE
This symptom is limited only when the diagnosis code is correct.
NG
Replace the hydraulic unit.
NG
Replace the torque transfer differential.
Check the trouble symptom.
NG
Replace AYC fluid.
OK
Correct
Check the trouble symptom.NO
Replace the torque transfer differential.
OK
Is foreign matter trapped in the hydrau-
lic line?YES
Repair
Check the AYC for operation..
(Refer to P.27-34.)OKCheck the AYC fluid.
NG
Check hydraulic pressure.
(Refer to P.27-35.)NGBleed the system of air..
(Refer to P.27-34.)