Mitsubishi Lancer (4A9 engine). Manual - part 53

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-65

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.

• Missing wheel speed sensor signal

• Wheel speed sensor signal continuously indi-

cates low 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

• Wheel bearing malfunction

• Deformation of the wheel speed detection 

encoder

• Adhesion of foreign materials on the wheel speed 

detection encoder

• Malfunction of wheel speed sensor

• Improper installation of the wheel speed sensor

• ASC-ECU malfunction

• 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.C102B 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.C102B 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.

• Rotate only two wheels with drum tester

DIAGNOSIS 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.C1044 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. C102B is also set.

Q: Is the diagnosis code No. C102B also set?

YES : 

Perform the diagnosis for the diagnosis 

code No. C102B (Refer to 

P.35C-31

).

NO : 

Go to Step 4.

STEP 4. Check for wheel speed sensor <RR> 
installation
Check how the wheel speed sensor <RR> is 
installed (Disconnection of wheel speed sensor 
<RR>, loose mounting bolt, etc.).

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

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

P.35C-188

). Then go to 

Step 5.

STEP 5. Check for wheel speed sensor <RR> 
output current
Refer to 

P.35C-179

.

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Replace the wheel speed sensor <RR> 
(Refer to 

P.35C-188

). Then go to Step 9.

STEP 6. Check for wheel bearing looseness
NOTE: 

.

•

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

•

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

−

 Wheel Bearing Axial Play 

Check ).

Q: Is the check result normal?

YES : 

Go to Step 7.

NO : 

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

− Rear axle hub 

assembly ). Then go to Step 10.

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-66

STEP 7. 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 8.

NO (Adhesion of foreign materials) : 

Remove the 

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

NO <Deformation> : 

Replace the rear wheel hub 

assembly <RR> (Refer to GROUP 27 

− 

Rear axle hub assembly ). Then go to Step 
10.

STEP 8. 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 diagnosis code No. C1044 set?

YES : 

Replace the wheel speed sensor <RR> 

(Refer to 

P.35C-188

). Then go to Step 9.

NO : 

Intermittent malfunction (Refer to GROUP 
00 

− How to Use Troubleshooting/How to 

Cope with Intermittent Malfunctions ).

STEP 9. 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 diagnosis code No. C1044 set?

YES : 

Replace the hydraulic unit (integrated with 

ASC-ECU) (Refer to 

P.35C-185

). Then go 

to Step 10.

NO : 

This diagnosis is complete.

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 diagnosis code No. C1044 set?

YES : 

Return to Step 1.

NO : 

This diagnosis is complete.

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-67

Code No. C1046 FL wheel speed sensor control phase time exceeded

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

AC612690

AP

Connector: A-08 <LHD>

A-08 (B)

AC701238 AE

Connectors: A-08, A-58 <RHD>

A-58 (B)

A-08 (B)

AC612691

AO

Connector: A-58 <LHD>

A-58 (B)

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-68

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
This diagnosis code is set if any malfunction below is 
found:

• When the brake fluid pressure is decreased for a 

long time.

• When the brake fluid pressure is held for a long 

time.

PROBABLE CAUSES

• Damaged wiring harness and connectors

• External noise interference

• Malfunction of wheel speed sensor

• ASC-ECU malfunction

• Excessive gap between the wheel speed sensor 

and the magnetic encoder for wheel speed detec-
tion

• Adhesion of foreign materials on the wheel speed 

sensor

• Adhesion of foreign materials on the magnetic 

encoder for wheel speed detection

• Wheel bearing malfunction

• Improper installation of the wheel speed sensor

• Deformation of the magnetic encoder for wheel 

speed detection

• Disturbance of magnetization pattern for mag-

netic encoder for wheel speed detection

• Missing teeth of the magnetic encoder for wheel 

speed detection

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.C1046 set?

YES : 

Go to Step 3.

NO : 

This diagnosis is complete.

STEP 3. M.U.T.-III diagnosis code
Check that the diagnosis codes No.C100A, C1011, 
C1014, and C1041 are also set.

Q: Are the diagnosis codes No.C100A, C1011, C1014, 

and C1041 also set?
YES : 

Carry out the diagnosis for the relevant 

diagnosis codes.

NO : 

Go to Step 4.

STEP 4. M.U.T.-III data list
Check the following data list (Refer to 

P.35C-172

).

• Item No.01: FL wheel speed sensor

Q: Is the check result normal?

YES : 

Go to Step 11.

NO : 

Go to Step 5.