Page 211 of 558
REAR AXLE – Troubleshooting 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.
Page 212 of 558
REAR AXLE – Troubleshooting 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.
Page 213 of 558
REAR AXLE – Troubleshooting 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.
Page 214 of 558
REAR AXLE – Troubleshooting 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
Page 215 of 558
REAR AXLE – Troubleshooting 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?YESCheck 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
Page 216 of 558
REAR AXLE – Troubleshooting 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
Page 217 of 558
REAR AXLE – Troubleshooting 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
Page 218 of 558
REAR AXLE – Troubleshooting 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
