check engine MITSUBISHI LANCER EVOLUTION IV 1998 Repair Manual

REAR AXLE – Special Tools / Troubleshooting <AYC>27-5
MB990988NumberNameO.D. mm
1MB990551Box–
2MB990989Base–
3(MB990990)Tool A25
(MB990991)Tool B28
(MB990992)Tool C31
MB990925
Brass bar
Bar (one-touch type)Toolbox
Installer adapter
Tool number (MB990925)O.D. mmTool number (MB990925)O.D. mm
AMB99092639.0AMB99093363.5
MB99092745.0MB99093467.5
MB99092849.5MB99093571.5
MB99092951.0MB99093675.5
MB99093054.0MB99093779.0
MB99093157.0BMB990938–
MB99093261.0CMB990939–
TROUBLESHOOTING <AYC>
1. BASIC TROUBLESHOOTING CONDITIONS
Before starting the troubleshooting procedure, make sure that the following items have been checked
okay.

The correct steering wheel has been properly installed in the neutral position of the steering column
shaft.

Tire and wheel sizes are correct with correct specifications. Inflation pressure, balance, and wear
conditions are okay.

Wheel alignment is correct.

The engine, suspension, and other parts have not been remodeled so as to affect the AYC system.
2. DIAGNOSIS FUNCTION
READING THE DIAGNOSIS CODE
Read the diagnosis code using AYC warning lamp.

REAR AXLE – Troubleshooting <AYC>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 <AYC>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 <AYC>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 – On-vehicle Service <Vehicles with AYC>27-31
7. SPEED SENSOR OUTPUT VOLTAGE
MEASUREMENT <VEHICLES WITHOUT
ABS>
(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 speed sensor as necessary.
Excessive clearance between the pole piece and rotor
of the speed sensor
Defective speed sensor
Waveform Check Using Oscilloscope
Check the harness and connector of the speed sensor for
connection. Then, use an oscilloscope to check for output
voltage waveform of each speed 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 <Vehicles with AYC>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

BASIC BRAKE SYSTEM – General / On-vehicle Service35A-2
GENERAL
OUTLINE OF CHANGE

The service procedures for left-hand drive vehicles have been established as described below.

The service procedures for the front and rear disc brakes have been changed since they had been
replaced by a different type. <EVOLUTION-VI with BREMBO braking system>
ON-VEHICLE SERVICE
BRAKE PEDAL CHECK AND ADJUSTMENT
<L.H. DRIVE VEHICLES>
1. Turn up the carpet, etc under the brake pedal.
2. Measure the brake pedal height as illustrated. If the brake
pedal height is not within the standard value, follow the
procedure below.
Standard value: 163.5 –166.5 mm
(1) Disconnect the stop lamp switch connector.
(2) Adjust the brake pedal height by turning the operating
rod with pliers (with the operating rod lock nut
loosened), until the correct brake pedal height is
obtained.
(3) Secure by tightening the lock nut of the operating
rod.
(4) Push the stop lamp switch in the direction of the
pedal stroke until it stops. (The switch will slide if
it is pushed firmly.)
(5) Lift up the pedal until the operating rod is fully
extended, and then slide the stop lamp switch back
to the required position. Adjust the position of the
switch by turning it until the distance shown in the
illustration is correct.
(6) Connect the connector of the stop lamp switch.
(7) Check that the stop lamp is not illuminated with the
brake pedal unpressed.
3. With the engine stopped, depress the brake pedal two
or three times. After eliminating the vacuum in the power
brake booster, press the pedal down by hand, and confirm
that the amount of movement before resistance is met
(the free play) is within the standard value range.
Standard value: 3 – 8 mmOperating
rod
Operating
rod lock nutStop lamp
switch
Pedal down
Pedal up
Lock nut
Lock nut
Outer case
0.5 – 1.0 mm

BASIC BRAKE SYSTEM – On-vehicle Service35A-3
If the free play exceeds the standard value, it is probably
due to excessive play between the retaining ring bolt
and brake pedal arm.
Check for excessive clearance and replace faulty parts
as required.
4. Start the engine, depress the brake pedal with
approximately 490 N of force, and measure the clearance
between the brake pedal and the floorboard.
Standard value: 80 mm or more
If the clearance is outside the standard value, check for
air trapped in the brake line, clearance between the lining
and the drum and dragging in the parking brake.
Adjust and replace defective parts as required.
5. Turn back the carpet, etc.

ABS – Troubleshooting35B-5
Code No.16: ABS-ECU power supply system (abnormal
voltage drop or rise)Probable cause
This code is output if the ABS-ECU or valve relay power supply voltage drops below
or rises above the rated values.
The valve relay power supply voltage is detected based on the voltage in the valve
relay monitor line.
Malfunction of battery

Malfunction of wiring harness or connector

Malfunction of valve relay

Malfunction of ABS-ECU
Caution
If battery voltage drops or rises during inspection, this code will be output as well, making it
impossible to obtain correct diagnostic results.
Before carrying out the following inspection, check the battery level, and refill it if necessary.
OK
Replace ABS-ECU.
OK
Replace the ABS-ECU.
OK
Check the trouble symptom.NGCheck the harness wire, and repair
if necessary.

Between ignition switch and
ABS-ECU
OK
Check the trouble symptom.NGCheck the harness wire, and repair
if necessary.

Between general-purpose fuse
No. 6 and valve relay
NG
Repair
OK
Check the harness wire for short
circuit, and repair if necessary.

Between valve relay and hydraulic
unit

Between valve relay and motor
relayNG
Repair OK
NG
Check the harness wire, and repair
if necessary.

Between valve relay and ABS-ECUNG
Repair
OK
Check the trouble symptom.
OK
Check the trouble symptom.NGCheck the harness wire, and repair
if necessary.

Between general-purpose fuse
No. 6 and valve relay
OK
Measure at the ABS-ECU connector
B-25.

Connector connected

Ignition switch: ON
(1) Voltage between 37 and body
ground
OK:Battery voltage
(2) Voltage between 48 and body
ground
OK:Battery voltage(1) NGCheck the following connectors:
A-76, B-25NG
Repair
(2) NG
Check the following connectors:
A-76, B-25NG
Repair
OK
Check the valve relay.NG
Replace
OK
Check the trouble symptom.NGCheck the harness wire, and repair
if necessary.

Between fusible link No. 8 and
valve relay
OK
Measure at the valve relay connector
A-76.

Disconnect the connector, and
measure at the harness side
connector.

Ignition switch: ON
(1) Voltage between 6 and body
ground
OK:Battery voltage
(2) Voltage between 2 and body
ground
OK:Battery voltage(1) NGCheck the following connector:
A-76NG
Repair
(2) NGCheck the following connector:
A-76NG
Repair
Measure at the ABS-ECU connector
B-24.

Disconnect the connector, and
measure at the harness side
connector.

Start the engine.

Voltage between 13 and body
ground
OK:Battery voltageNGCheck the following connectors:
B-24, B-52, B-74, B-76NG
Repair

ABS – TroubleshootingABS – Troubleshooting35B-6
Code No. 27: AYC monitor system (defective AYC)Probable cause
This code is output when the AYC monitor signal becomes faulty.
Defective AYC-ECU

Defective ABS-ECU

Defective harness or connector
OK
Replace the ABS-ECU.
OK
MUT-II data list
AYC signal
OKOFF to be displayed when the
engine runs at idle with the
vehicle stationary.NGReplace AYC-ECU.
OK
Check the harness between ABS-ECU
and AYC-ECU.NG
Repair
Check the following connectors:
B-25, B-96NG
Repair
Code No. 32: Acceleration sensor (longitudinal accelera-
tion) circuit systemProbable cause
This code is output under either of the following conditions:

The output from the acceleration sensor (longitudinal acceleration) becomes 0.5
V or less, or 4.5 V or more.

The acceleration sensor (longitudinal acceleration) harness is open- or
short-circuited.
Defective acceleration sensor (longitudinal accelera-
tion)

Defective harness or connector

Defective ABS-ECU
OK
Check the trouble symptom.NGReplace ABS-ECU.
OK
Check the trouble symptom.NGCheck and repair the harness between
acceleration sensor (longitudinal
acceleration) and ABS-ECU.
OK
Check the trouble symptom.NGCheck and repair the harness between
general-purpose fuse No. 6 and
acceleration sensor (longitudinal
acceleration).
OK
Replace ABS-ECU.
OK
Check the following connector:
B-24NG
Repair
OK
Measure at B-24 ABS-ECU connector.

Connect the connector.

Ignition switch: ON

Voltage across 4 and 17
OK:2.4 – 2.6 V
(horizontal position)NGCheck the following connectors:
B-24, D-20, B-52NG
Repair
NG
Check the harness between accelera-
tion sensor (longitudinal acceleration)
and ABS-ECU.NG
Repair
OK
Check the trouble symptom.
OK
Check the valve relay.NG
Replace
(1) NGCheck the following connectors:
D-20, B-49, B-75NG
Repair
Check the following connector:
D-20, B-49, B-75NG
Repair
(2) NG
Measure at D-20 acceleration sensor
(longitudinal acceleration) connector.

Disconnect the connector and
measure at the harness side.

Ignition switch: ON
(1) Voltage across 1 and body ground
OK:Battery voltage
(2) Continuity across 3 and body
ground
OK:Conducting