1998 MITSUBISHI LANCER EVOLUTION IV battery

REAR AXLE – Troubleshooting 27-7
4. INSPECTION PROCEDURES FOR DIAGNOSIS CODES
Code No. 12: Power supply voltage (valve power supply)
systemProbable cause
This code is output when the AYC-ECU power supply voltage drops below, goes
beyond, a specified level.
Defective harness or connector

Defective battery

Defective AYC-ECU
NOTE
Refer to the corresponding item if any other diagnosis code is being output.
Is the battery voltage correct?NG
Replace
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:Battery voltageNGCheck the following connectors:
B-96, B-94, B-49, B-75, B-76
OK
Check the trouble symptom.
NG
Check and repair harness between
ignition switch (IG
2) and AYC-ECU. OKReplace AYC-ECU.NG
Repair
Code No. 21, 22, 23, 24: Wheel speed sensor systemProbable cause
This code is output if any one of three wheel speed sensors fails to provide an input
even after the other wheel exceeded 8 km/h.
Defective harness or connector

Defective ABS-ECU

Defective AYC-ECU

OK
Replace AYC-ECU.
OK
Replace ABS-ECU.
NG
Check harness between AYC-ECU
and ABS-ECU.NG
Repair
OK
Check the trouble symptom.
Is an ABS diagnosis code No. 21, 22,
23, or 24 output?YESTroubleshooting
NO
Measure at B-95 AYC-ECU connector.

Disconnect the connector and
measure at the harness side.

Ignition switch: ON

Turn tire at 1/2 to 1 revolution/sec.

Voltage across 6/7/8/9 and body
ground
OK:42 mV or more (when mea-
sured with a circuit tester)
120 mV-P or more (when
measured with an oscillo-
scope)OKCheck the following connector:
B-95
OK
Check the trouble symptom.
NG
Check the following connectors:
B-24, B-95NG
RepairNG
Repair

REAR AXLE – Troubleshooting 27-13
Code No. 41: TPS systemProbable cause
This code is output when the input from the throttle position sensor falls short of
0.2 V.
Defective TPS

Defective harness or connector

Defective AYC-ECU
OK
Replace AYC-ECU.
NG
Check and repair the harness between
AYC-ECU and TPS.
OK
Check the trouble symptom.
NO
Measure at B-95 AYC-ECU connector.

Connector connected.

Ignition switch: ON

Voltage across 18 and body ground

Fully open the throttle valve.
OK:4.5 – 5.0 VNGCheck the following connector:
B-95
Is the MPI diagnosis code No. 14 out-
put?YESRefer to GROUP 13 TROUBLE-
SHOOTING.
NG
Repair
Code No. 51: Longitudinal acceleration sensor systemProbable cause
Code No. 56: Lateral acceleration sensor system
This code is output when the output from the acceleration sensor becomes 0.5 V
or less or 4.5 V or more.
Defective longitudinal acceleration sensor

Defective lateral acceleration sensor

Defective harness or connector

Defective AYC-ECU
NG
Replace the acceleration sensor.
OK
Check the trouble symptom.
OK
Check and repair the harness between
acceleration sensor and ignition
switch.
OK
Check the trouble symptom.
NG
Check and repair the harness between
acceleration sensor and AYC-ECU.
NGReplace AYC-ECU.
OK
Check the following connectors:
D-20, D-32
OK
Check the trouble symptom.
OK
Check the trouble symptom.
NG: 4.5 V or more
Check the acceleration sensor. (Refer
to P.27-54.)NG
Replace
NG: 0.5 V or less
Check at D-20, D-32 acceleration sen-
sor connector.

Disconnect the connector and
measure at the harness side.

Ignition switch: ON

Voltage across 1 and body ground
OK:Battery voltageNGCheck the following connectors:
D-20, D-32, B-49, B-75, B-76NG
Check and repair the harness between
acceleration sensor and AYC-ECU.
NG
Measure at D-20, D-32 acceleration
sensor connector.

Connector connected.

Ignition switch: ON

Voltage across 2 and body ground
OK:0.5 – 4.5 VOKCheck the following connectors:
D-20, D-32NG
Repair
Measure at B-95 AYC-ECU connector.

Connector connected.

Ignition switch: ON

Voltage across 1/3 and body
ground
OK:0.5 – 4.5 VOKCheck the following connector:
B-95NG
Repair

REAR AXLE – Troubleshooting 27-19
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.27-29.)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: Battery voltage
NG
NO
Can pump be operated?YESMeasure 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:Battery voltage
YES
Is diagnosis code no. 81 output?YESCheck the AYC relay system. (Refer to P.27-18.)
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.27-52.)

Check AYC motor for
operation.NG
Repair

REAR AXLE – Troubleshooting 27-20
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:Battery 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.27-15.)

Check the directional control valve
(right) system (code no. 72).
(Refer to P.27-16.)

Check the directional control valve
(left) system (code no. 73).
(Refer to P.27-17.)
(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.27-52.)NG
Repair

REAR AXLE – Troubleshooting 27-21
5. INSPECTION CHART FOR TROUBLE SYMPTOMS
Trouble symptomInspection
procedure No.Ref. page
AYC warning lamp does not light up when the ignition key is turned to “ON” (engine
stationary).127-21
AYC warning lamp remains lit up after the engine has started.227-22
AYC is inoperative.
Unable to start or accelerate on slippery road surfaces.327-22
Rear tires are noisy during low-speed cornering.
Vehicle skews.427-23
6. INSPECTION PROCEDURE FOR TROUBLE SYMPTOMS
INSPECTION PROCEDURE 1
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:Battery voltageNGCheck the following connectors:
B-08, B-74, B-76NG
Repair

REAR AXLE – Troubleshooting 27-24
7. CHECK AT AYC-ECU TERMINALS
7-1 TERMINAL VOLTAGE LISTING
(1) The voltage is to be measured across each terminal and ground terminal.
(2) Fig. below shows the arrangement of the terminals.
Terminal
No.Check itemCheck requirementNormally
1Lateral acceleration sensorIgnition switch: ON2.4 – 2.6 V
(horizontal position)
2Longitudinal acceleration
sensor ground
Lateral acceleration sensor
groundAt all times0 V
3Longitudinal acceleration
sensorIgnition switch: ON2.4 – 2.6 V
(horizontal position)
4Steer sensor (ST-2)Engine: Idle speed
Turn steering wheel slowly.0 V ↔ approx. 3 V
flashing
5Steer sensor (ST-1)Engine: Idle speed
Turn steering wheel slowly.0 V ↔ approx. 3 V
flashing
6*1FR wheel speedVehicle stationary1 V or less
Forward vehicle slowly.0 – 5 V
7*1FL wheel speedVehicle stationary1 V or less
Forward vehicle slowly.0 – 5 V
8*1RR wheel speedVehicle stationary1 V or less
Forward vehicle slowly.0 – 5 V
9*1FL wheel speedVehicle stationary1 V or less
Forward vehicle slowly.0 – 5 V
10Diagnosis selection inputBattery voltage
11Stop lamp switchIgnition switch:
ON
Stop lamp switch: ONBattery voltage
ON
Stop lamp switch: OFF1 V or less
12*1ABS monitorWhen ABS monitor is activatedBattery voltage
When ABS monitor is deactivated1 V or less
17Steer sensor (ST-N)Engine:
Idle speed
Steering wheel: Neutral position0.5 V or less
Idle speed
Steering wheel: Turned 90 from
neutral position2.5 – 3.5 V

REAR AXLE – Troubleshooting 27-25
Terminal
No.Normally Check requirement Check item
18TPSIgnition switch:
ON
Accelerator pedal: Fully closed0.3 – 1.0 V
ON
Accelerator pedal: Fully open4.5 – 5.0 V
23Diagnosis data input/output1 V or less
24Idle position switchIgnition switch:
ON
Accelerator pedal: Fully closed2 V or less
ON
Accelerator pedal: Fully open4.5 – 5.0 V
25Accumulator pressure
switchIgnition switch:
ONAccumulator internal pressure:
Low2 V or less
Accumulator internal pressure:
HighBattery voltage
26ECU groundAt all times0 V
31AYC-ECU power supplyIgnition switch: ONBattery voltage
Ignition switch: OFF0 V
35AYC motor relayIgnition switch:
ON
When motor is energizedBattery voltage
ON
When motor is deenergized2 V or less
36AYC warning lampIgnition switch:
ON
When lamp is OFFBattery voltage
ON
When lamp is ON2 V or less
37Directional control valve
(right)
Ignition switch:
ON
Right clutch: ONBattery voltage
(right)ON
Right clutch: OFF0 V
38Proportioning valveIgnition switch:
ONAYC-ON0 V to battery volt-
age
AYC-OFF0 V
39ECU backup power supplyAt all timesBattery voltage
45Directional control valve
(left)
Ignition switch:
ON
Left clutch: ONBattery voltage
(left)ON
Left clutch: OFF0 V
46ECU groundAt all times0 V
NOTE
*1: Indicates the vehicles with ABS.

REAR AXLE – On-vehicle Service 27-32
Waveform Observation Points
SymptomProbable causeAction
Waveform amplitude is too small, or no
waveform.Defective 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 speed sensorCorrect sensor installation.
Missing or collapsed rotor toothReplace rotor.
Caution
Since the 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 speed
sensor output voltage waveform should therefore be checked also by rocking the sensor harness
so that driving on rough roads may be simulated.
8. 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