1998 MITSUBISHI LANCER EVOLUTION IV warning

REAR AXLE – Troubleshooting 27-10
Code No. 26: Wheel speed sensor system (faulty output
signal)Probable cause
This code is output if the speed of one of the four wheels exceeds a specified level
when the vehicle speed is 20 km/h or more. At this time, the warning lamp is turned
on.
Defective harness or connector

Defective AYC-ECU

Defective ABS-ECU

OK
Replace ABS-ECU.
NG
Check harness between AYC-ECU
and ABS-ECU.NG
Repair
NG
Replace AYC-ECU.
OK
Check the trouble symptom.
NG
Check the following connectors:
B-24, B-95NG
Repair
OK
Check the trouble symptom.
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)NGCheck the following connector:
B-95
Is ABS diagnosis code No. 15 output?YESTroubleshooting
NG
Repair

NG
Check and repair the harness between
speed sensor and AYC-ECU.
OK
Check the trouble symptom.
OK
Check the following connectors:
B-95, B-52, B-17, A-26, A-50, D-04,
D-14, D-19NG
Repair
OK
Check wheel bearing.NG
Replace
NG
Replace AYC-ECU.
OK
Check the trouble symptom.
OK
Check the following connector:
B-95NG
Repair
OK
Check speed sensor output voltage.
(Refer to P.27-31.)NGCheck speed sensor and rotor.
Check speed sensor for installation.NG
Repair
NG
Replace

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 27-22
INSPECTION PROCEDURE 2
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 AYC-ECU power supply is 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 3
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.OKCheck the AYC fluid.
NG
Add hydraulic oil.
NG
Check hydraulic pressure.NGBleed the system of air.
Check the hydraulic oil level.NGCheck for oil leak.OK
Repair

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

ABS – Troubleshooting35B-8
Code No. 51: Valve relay systemProbable cause
This code is output under any of the following conditions:

The solenoid valve power is not supplied when ABS-ECU attempts to turn ON
the valve relay as part of the initial check when the ignition switch is turned ON.

The solenoid valve power remains supplied when ABS-ECU attempts to turn OFF
the valve relay as part of the initial check when the ignition switch is turned ON.

The solenoid valve power is not supplied while the valve relay remains ON under
normal conditions.
Defective ABS valve relay

Defective harness or connector

Defective ABS-ECU
NOTE
In the diagnosis code reading by means of the ABS warning lamp, this code is output in addition to
the actual diagnosis code since the valve relay connector is disconnected.
If the ABS warning lamp turns ON even when the spot represented by the diagnosis code output in
addition to this code has been repaired, and if no diagnosis code other than No. 51 is output, then
the valve relay system is probably defective. Make the following checks.
OK
Check the trouble symptom.NGCheck and repair the harness between
general-purpose fuse No. 6 and valve
relay.
NG
Replace the ABS-ECU.
OK
Check the trouble symptom.
OK
Check the trouble symptom.NGCheck and repair the harness between
valve relay and ABS-ECU.
OK
Check the following connectors:
A-76, B-25NG
Repair
OK
Measure at A-76 valve relay connector
and B-25 ABS-ECU connector.

Disconnect the connector and
measure at the harness side.

Continuity across the following
terminals
OK:Conducting
Valve relay ABS-ECU
side side
3–48
5–37NGCheck the following connectors:
A-76, B-25NG
Repair
OK
Check the trouble symptom.NGCheck and repair the harness between
fusible link No. 8 and valve relay.
OK
Measure at A-76 valve relay connector.

Disconnect the connector and
measure at the harness side.

Ignition switch: ON
(1) Voltage across 6 and body ground
(2) Voltage across 2 and body ground
OK:Battery voltage(1) NGCheck the following connector:
A-76NG
Repair
(2) NG
Check the following connector:
A-76NG
Repair
Check the valve relay.NG
Replace

ABS – Troubleshooting35B-11
3. INSPECTION CHART FOR TROUBLE SYMPTOMS
Get an understanding of the trouble symptoms and check according to the inspection procedure chart.
Trouble symptomsInspection pro-
cedure No.Reference page
When the ignition key is turned to “ON” (engine stopped), the ABS warning lamp
does not illuminate.135B-12
Even after the engine is started, the ABS warning lamp remains illuminated.235B-13
After the ignition key is turned to “ON”, the ABS warning lamp blinks twice, and
when turned to “START”, it illuminates. When returned to “ON”, the lamp
flashes once, and then switches off.335B-13
When the ignition key is turned to “START”, the ABS warning lamp does not
illuminate.435B-14
Brake operation is abnormal535B-14
Caution
(1) If steering movements are made when driving at high speed, or when driving on road surfaces
with low frictional resistance, or when passing over bumps, the ABS may operate even though
sudden braking is not being applied. Because of this, when getting information from the customer,
check if the problem occurred while driving under such conditions as these.
(2) During ABS operation, the brake pedal may vibrate or may not be able to be depressed. Such
phenomena are due to intermittent changes in hydraulic pressure inside the brake line to prevent
the wheels from locking and is not an abnormality.

ABS – Troubleshooting35B-12
4. INSPECTION PROCEDURE FOR TROUBLE SYMPTOMS
INSPECTION PROCEDURE 1
When the ignition key is turned to “ON” (engine stopped),
the ABS warning lamp does not illuminate.
Probable cause
The ABS-ECU turns the valve relay ON → OFF → ON for initial checking when
it is powered ON. Accordingly, the ABS warning lamp illuminates twice even if the
circuit between the ABS warning lamp and ABS-ECU is faulty.
The cause may be an open circuit in the lamp power supply circuit, a blown lamp,
an open circuit between the ABS warning lamp and ABS-ECU or between the ABS
warning lamp and the valve relay.
Blown fuse

Burn out ABS warning lamp bulb

Malfunction of wiring harness or connector
OK
Check the trouble symptom.NGReplace the combination meter.
OK
Check the following connectors:
B-08, B-09NG
Repair
OK
Check the trouble symptom.NGCheck the harness wire, and repair
if necessary.

Between ignition switch and ABS
warning lamp
OK
Check the motor for operation.NGCheck the harness wire, and repair
if necessary.

Between ABS warning lamp and
ABS-ECU

Between ABS warning lamp and
valve relay
OK
Check the following connectors:
A-76, B-09, B-52NG
Repair
OK
Measure at the combination meter con-
nector B-09.

Disconnect the connector, and
measure at the combination meter
side connector.

Ignition switch: ON

ABS warning lamp condition when
terminal 12 is grounded.
OK:IlluminatesNGCheck whether the ABS warning lamp
bulb is burnt out.NG
OK
Measure at the combination meter con-
nector B-08.

Disconnect the connector and
measure at the harness side
connector.

Ignition switch: ON

Voltage between 42 and body
ground
OK:Battery voltageNGCheck the following connectors:
B-08, B-75, B-76NG
Repair
Fuse check
General-purpose fuse No.4NGReplace fuse after eliminating the
cause.
Replace the ABS warning lamp bulb.