Mitsubishi Lancer (4A9 engine). Manual — part 48

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-45

• ASC-ECU malfunction

• Disturbance of magnetisation pattern for wheel

speed detection encoder

• The number of poles on the Magnetic encoder for

wheel speed detection (N-pole and S-pole) is
changed

Past trouble

• When diagnosis code No.C1020 is also set, carry

out diagnosis with particular emphasis on wiring
harness and connector failures between ASC-
ECU and the wheel speed sensor. For diagnosis
procedures, refer to How to treat past trouble
(GROUP 00

− How to Use Troubleshooting/How

to Treat Past Trouble ).

• When diagnosis code No.C1020 is not set, the

following conditions may be present:

• Some wheels slip

• Unstable vehicle attitude

• External noise interference

• Vehicle ran with the parking brake applied.

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnosis
Use M.U.T.-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES :

Go to Step 3.

NO :

Repair the CAN bus lines (Refer to GROUP
54C

− CAN Bus Diagnostics Table ). On

completion, go to Step 2.

STEP 2. Diagnosis code recheck after resetting
CAN bus lines

Q: Is the diagnosis code No.C1027 set?

YES :

Go to Step 3.

NO :

This diagnosis is complete.

STEP 3. M.U.T.-III diagnosis code
Check that the diagnosis code No. C1020 is also set.

Q: Is the diagnosis code No. C1020 also set?

YES :

Perform the diagnosis for the diagnosis

code No. C1020 (Refer to

P.35C-27

).

NO :

Go to Step 4.

STEP 4. Connector check: A-58 ASC-ECU
connector, C-31 intermediate connector, D-17
intermediate connector, F-24 rear wheel speed
sensor <LH> connector

Q: Is the check result normal?

YES :

Go to Step 5.

NO :

Repair the defective connector. Then go to
Step 12.

STEP 5. Wiring harness check between A-58
ASC-ECU connector terminal No.36 and F-24 rear
wheel speed sensor <LH> connector terminal
No.1, and between A-58 ASC-ECU connector
terminal No.37 and F-24 rear wheel speed sensor
<LH> connector terminal No.2.

Q: Is the check result normal?

YES :

Go to Step 6.

NO :

Repair the wiring harness. Then go to Step
12.

STEP 6. Check for wheel speed sensor <RL>
installation
Check how the wheel speed sensor <RL> is installed
(Disconnection of wheel speed sensor <RL>, loose
mounting bolt, etc.).

Q: Is the check result normal?

YES :

Go to Step 7.

NO :

Reinstall the wheel speed sensor <RL>
correctly (Refer to

P.35C-188

). Then go to

Step 7.

STEP 7. Check for wheel speed sensor <RL>
output current
Refer to

P.35C-179

.

Q: Is the check result normal?

YES :

Go to Step 8.

NO :

Replace the wheel speed sensor <RL>
(Refer to

P.35C-188

). Then go to Step 11.

STEP 8. Check for wheel bearing looseness
NOTE:

.

•

Loose wheel bearing may increase the gap
between the wheel speed sensor <RL> and the
wheel speed detection magnet encoder.

•

Check the Rear wheel hub assembly <RL>
(Refer to GROUP 27

−

Wheel Bearing Axial Play

Check ).

Q: Is the check result normal?

YES :

Go to Step 9.

NO :

Replace the rear wheel hub assembly <RL>
(Refer to GROUP 27

− Rear axle hub

assembly ). Then go to Step 12.

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-46

STEP 9. Check of wheel speed detection encoder

AC700162

Rear hub

Oil seal

Ball bearing

Magnetic
encoder

AB

Check the encoder for adhesion of foreign materials
or deformation.

Q: Is the check result normal?

YES :

Go to Step 10.

NO (Adhesion of foreign materials) :

Remove the

foreign materials and clean the encoder so
as not to disturb the magnetization pattern
on it while taking care of the magnet,
magnetic substance, and magnetic
attraction. Then go to Step 12.

NO (Deformation) :

Replace the rear wheel hub

assembly <RL> (Refer to GROUP 27

−

Rear axle hub assembly ). Then go to Step
12.

STEP 10. Check whether the diagnosis code is
reset.
(1) Erase the diagnosis code.
(2) Drive the vehicle at 20 km/h or higher.

NOTE: The ABS warning lamp does not turn OFF
in some cases unless the vehicle runs at 20 km/h
or higher.

Q: Is the diagnosis code No.C1027 set?

YES :

Replace the wheel speed sensor <RL>

(Refer to

P.35C-188

). Then go to Step 11.

NO :

Intermittent malfunction (Refer to GROUP
00

− How to Use Troubleshooting/How to

Cope with Intermittent Malfunctions).

STEP 11. Check whether the diagnosis code is
reset.
(1) Erase the diagnosis code.
(2) Drive the vehicle at 20 km/h or higher.

NOTE: The ABS warning lamp does not turn OFF
in some cases unless the vehicle runs at 20 km/h
or higher.

Q: Is the diagnosis code No.C1027 set?

YES :

Replace the hydraulic unit (integrated with

ASC-ECU) (Refer to

P.35C-185

). Then go

to Step 12.

NO :

This diagnosis is complete.

STEP 12. Check whether the diagnosis code is
reset.
(1) Erase the diagnosis code.
(2) Drive the vehicle at 20 km/h or higher.

NOTE: The ABS warning lamp does not turn OFF
in some cases unless the vehicle runs at 20 km/h
or higher.

Q: Is the diagnosis code No.C1027 set?

YES :

Return to Step 1.

NO :

This diagnosis is complete.

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-47

Code No. C1032 Abnormality in RR wheel speed sensor signal

Wheel Speed Sensor Circuit

ASC-ECU

(LH)

(LH)

(RH)

(RH)

FRONT WHEEL SPEED SENSOR

REAR WHEEL SPEED SENSOR

Wire colour code
B : Black LG : Light green G : Green L : Blue W : White Y : Yellow SB : Sky blue
BR : Brown O : Orange GR : Grey R : Red P : Pink V : Violet PU : Purple SI : Silver

ACB02565

AC612691

AO

Connector: A-58 <LHD>

A-58 (B)

AC701238 AF

Connector: A-58 <RHD>

A-58 (B)

ACB02572

AB

Connector: C-67 <LHD>

ACA00895

ACA00895AT

Connector: C-67 <RHD>

AC612723

AL

Connector: D-12

AC612744 BI

Connector: F-04 <LANCER>

(B)

AC801775BN

(B)

Connector: F-04 <LANCER SPORTBACK>

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-48

CAUTION

• If there is any problem in the CAN bus lines,

an incorrect diagnosis code may be set. Prior
to this diagnosis, diagnose the CAN bus lines
(Refer to GROUP 54C

− CAN Bus Diagnostics

Table ).

• Whenever ECU is replaced, ensure that the

CAN bus lines are normal.

• When the hydraulic unit (integrated with ASC-

ECU) is replaced, always carry out the calibra-
tion of the steering wheel sensor, the G and
yaw rate sensor and brake fluid pressure sen-
sor (Refer to

P.35C-182

,

P.35C-183

and

P.35C-

184

).

OPERATION

• The wheel speed sensor is a kind of a pulse gen-

erator. It consists of encoders (a plate on which
north and south pole sides of the magnets are
arranged alternately) for detecting the wheel
speed which rotates at the same speed of the
wheels and wheel speed sensors. This sensor
outputs frequency pulse signals in proportion to
the wheel speed.

• The pulse signals, which the wheel speed sensor

creates, are sent to ASC-ECU. ASC-ECU uses
the frequency of the pulse signals to determine
the wheel speed.

DIAGNOSIS CODE SET CONDITIONS
ASC-ECU monitors the signals from each wheel
speed sensor while the vehicle is being driven. If any
fault below is found in these sensor signals, ASC-
ECU will set the relevant diagnosis code.

• Irregular change in the wheel speed sensor sig-

nal

• Wheel speed sensor signal continuously indi-

cates high value.

PROBABLE CAUSES

Current trouble

• Excessive gap between the wheel speed sensor

and the wheel speed detection encoder

• Adhesion of foreign materials on the wheel speed

sensor

• Adhesion of foreign materials on the wheel speed

detection encoder

• Wheel bearing malfunction

• Malfunction of wheel speed sensor

• Damaged wiring harness and connectors

• External noise interference

• Improper installation of the wheel speed sensor

• Deformation of the wheel speed detection

encoder