Mitsubishi Lancer Evolution X. Manual - part 161

DIAGNOSIS

TSB Revision

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-109

NOTE: ASC controls the vehicle based on the wheel speed sig-
nal. When the brake fluid pressure is decreased or held for an 
abnormally long time, the wheel speed sensor signal may have 
a problem.

.

PROBABLE CAUSES

• Damaged wiring harness and connectors
• External noise interference
• Malfunction of wheel speed sensor
• ABS-ECU malfunction
• 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
• Improper installation of the wheel speed sensor
• Deformation of the wheel speed detection encoder
• Disturbance of magnetization pattern for wheel speed 

detection encoder

• Missing teeth of the wheel speed detection encoder

DIAGNOSIS

Required Special Tools:

• MB991958 Scan Tool (M.U.T.-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)
• MB991827 M.U.T.-III USB Cable
• MB991910 M.U.T.-III Main Harness A

• MB991997: ASC check harness

STEP 1. Using scan tool MB991958, diagnose the CAN bus 
lines.
Using scan tool MB991958, 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 − 

Troubleshooting 

P.54C-15

.) After repairing the CAN 

bus line, go to Step 2.

STEP 2. DTC recheck after repairing the CAN bus line
Q: Is DTC C1048 set?

YES : Go to Step 3.
NO :  This diagnosis is complete.

STEP 3. Scan tool diagnostic trouble code
Check that DTC No. C1020, C1027, C102A, and C1043 are 
simultaneously set.
Q: Are DTC C1020, C1027, C102A and C1043 also set?

YES : Carry out the diagnosis for the diagnostic trouble 

codes that are set, and then go to Step 5.

NO :  Go to Step 4.

DIAGNOSIS

TSB Revision

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-110

STEP 4. Scan tool service data
Check the following service data. (Refer to 

P.35C-276

.)

• Item No.03: RL wheel speed sensor

Q: Is the check result normal?

YES : Go to Step 16.
NO :  Go to Step 5.

STEP 5. Voltage measurement at A-05 ASC-ECU connector
(1) Disconnect the ASC-ECU connector, connect the special 

tool ASC check harness (MB991997) to the wiring 
harness-side connector, and then measure at the special 
tool connector side.
NOTE: Do not connect the special tool to ASC-ECU.

(2) Turn the ignition switch to the ON position.
(3) Measure the voltage between the wheel speed sensor 

power supply terminal (signal terminal) No. 36 and the body 
ground as well as between the ground terminal No. 37 and 
the body ground.

OK: 1 volt or less

Q: Is the check result normal?

YES  : Go to Step 6.
NO (Not normal at terminal No. 34 or 33) : Go to Step 7.

AC400817CH

ASC-ECU

MB991997

Check harness

A-05 ASC-ECU
harness connector

DIAGNOSIS

TSB Revision

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-111

STEP 6. Resistance measurement at A-05 ASC-ECU 
connector
(1) Disconnect the ASC-ECU connector, connect the special 

tool ASC check harness (MB991997) to the wiring 
harness-side connector, and then measure at the special 
tool connector side.
NOTE: Do not connect the special tool to ASC-ECU.

(2) Measure the resistance between the wheel speed sensor 

circuit power supply terminal (signal terminal) No. 36 and 
the body ground as well as between the ground terminal 
No. 37 and the body ground.

OK: No continuity

Q: Is the check result normal?

YES  : Go to Step 9.
NO (Not normal at the terminal No. 36 or 37) : Go to Step 

7.

STEP 7. Connector check: A-05 ASC-ECU connector, C-45 
intermediate connector, D-18 wheel speed sensor <RL> 
connector
Q: Is the check result normal?

YES : Go to Step 8.
NO :  Repair the defective connector. Then go to Step 17.

STEP 8. Wiring harness check between A-05 ASC-ECU 
connector terminal No. 36 and D-18 wheel speed sensor 
<RL> connector terminal No. 1, and between A-05 
ASC-ECU connector terminal No. 37 and D-18 wheel speed 
sensor <RL> connector terminal No. 2

• Short circuit check of wheel speed sensor <RL> circuit

Q: Is the check result normal?

YES : Replace the wheel speed sensor <RL>. (Refer to 

P.35C-300

.) Then go to Step 17.

NO :  Repair the wiring harness. Then go to Step 17.

AC400817CI

ASC-ECU

MB991997

Check harness

A-05 ASC-ECU
harness connector

DIAGNOSIS

TSB Revision

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-112

STEP 9. Voltage measurement at A-05 ASC-ECU connector
(1) Disconnect the ASC-ECU connector, connect the special 

tool ASC check harness (MB991997) to the ASC-ECU-side 
connector and the wiring harness-side connector, and then 
measure at the special tool connector side.

(2) Turn the ignition switch to the ON position.
(3) Measure the voltage between the wheel speed sensor 

circuit power supply terminal (signal terminal) No. 36 and 
the body ground.

OK: Battery positive voltage

Q: Is the check result normal?

YES : Go to Step 10.
NO :  Go to Step 12.

STEP 10. Wiring harness check between A-05 ASC-ECU 
connector terminal No. 36 and D-18 wheel speed sensor 
<RL> connector terminal No. 1, and between A-05 
ASC-ECU connector terminal No. 37 and D-18 wheel speed 
sensor <RL> connector terminal No. 2

• Open circuit check of wheel speed sensor <RL> circuit

Q: Is the check result normal?

YES : Go to Step 11.
NO :  Repair the wiring harness. Then go to Step 17.

STEP 11. Check of wheel speed sensor as a single unit
Refer to 

P.35C-303

.

Q: Is the check result normal?

YES : Go to Step 13.
NO :  Replace the wheel speed sensor <RL>. (Refer to 

P.35C-300

.) Then go to Step 17.

STEP 12. Connector check: A-05 ASC-ECU connector, 
C-45 intermediate connector, D-18 wheel speed sensor 
<RL> connector
Q: Is the check result normal?

YES : Go to Step 16.
NO :  Repair the defective connector. Then go to Step 17.

AC400817CJ

ASC-ECU

MB991997

Check harness

A-05 ASC-ECU
harness connector