Mitsubishi Evolution X. Manual - part 809

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-243

Inspection Procedure 11: ASC-ECU power supply circuit system

CAUTION

• When the ASC-ECU power supply voltage becomes 9.7 

± 0.3 V or less, the ABS warning light, ASC warning dis-

play, and ASC OFF display illuminate, and the ABS, 
skid control, and TCL controls are prohibited.

• If the battery terminal is not tightened properly, a dump 

surge may occur and the power supply voltage may 
become abnormally high for a short period of time.

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

rect diagnostic trouble code may be set. Prior to this 
diagnosis, diagnose the CAN bus lines.

• Whenever the ECU is replaced, ensure that the CAN 

bus lines are normal.

• When the hydraulic unit (integrated with ASC-ECU) is 

replaced, always perform the calibration of steering 
wheel sensor, G and yaw rate sensor, brake fluid pres-
sure sensor, cut valve, and inlet valve.(Refer to 

P.35C-266

, 

P.35C-267

, 

P.35C-268

, and 

P.35C-269

.)

.

AC708948

Connector: A-05

A-05 (B)

AB

AC708972AS

Connectors: C-309, C-315, C-317

ETACS-ECU

C-315

C-317

C-309 (B)

AC708950

Connectors: C-103, 130

AJ

C-103 (B)

C-130 (BR)

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-244

SYSTEM OPERATION

• ASC-ECU contains the power supply circuit (terminal No. 

32) for the solenoid valve. The solenoid valve is energized 
by the valve relay, which is incorporated in ASC-ECU.

• ASC-ECU contains the power supply circuit (terminal No. 1) 

for the pump motor. The pump motor is energized by the 
motor relay, which is incorporated in ASC-ECU.

• ASC-ECU contains the power supply circuit (terminal No. 2) 

for ASC-ECU, and the power is supplied from the fusible 
link No. 34 through the multi-purpose fuse No. 17.

• If a malfunction occurs in the ASC-ECU power supply, the 

communication with scan tool becomes unavailable.

.

PROBABLE CAUSES

• Damaged wiring harness and connectors

• Malfunction of fuse or fusible link

• Improper tightening of battery terminal

• Improper tightening of grounding bolt

• Battery failure

• Charging system failed

• ASC-ECU malfunction

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. Battery check
Refer to GROUP 54A 

− Battery Test 

P.54A-9

.

Q: Is the battery in good condition?

YES : Go to Step 3.
NO :  Charge or replace the battery. Then, go to Step 2.

STEP 2. Charging system check
Refer to GROUP 16 

− Output Current Test 

P.16-8

.

Q: Is the charging system in good condition?

YES : Go to Step 3.
NO :  Repair or replace the charging system component(s).

STEP 3. Connector check: A-05 ASC-ECU connector
Q: Is the check result normal?

YES : Go to Step 4.
NO  :  Repair the defective connector.

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-245

STEP 4. Voltage measurement at A-05 ASC-ECU connector
(1) Disconnect the connector, connect the ASC check harness 

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

(2) Measure the voltage between the terminal No. 32 and the 

body ground.

OK: System voltage

Q: Is the check result normal?

YES : Go to Step 7.
NO :  Go to Step 5.

STEP 5. Fusible link check: Check the fusible link No. 27.
Q: Is the check result normal?

YES : An open circuit may be present in the power supply 

circuit. Repair the wiring harness between A-05 
ASC-ECU connector terminal No. 32 and the fusible 
link No. 27.

NO :  Go to Step 6.

STEP 6. Wiring harness check between A-05 ASC-ECU 
connector and fusible link No. 27.
(1) Disconnect ASC-ECU connector A-05.
(2) Remove fusible link No. 27.
(3) Check the continuity (short to ground) between A-05 

ASC-ECU connector terminal No. 32 and the ground.

OK: No continuity

Q: Is the check result normal?

YES : Replace the fusible link No.27.
NO :  Short circuit may be present in the power supply 

circuit. Repair the wiring harness between A-05 
ASC-ECU connector terminal No. 32 and fusible link 
No. 27.

AC400817CN

ASC-ECU

MB991997

A-05 ASC-ECU 
harness connector

Check harness

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-246

STEP 7. Voltage measurement at A-05 ASC-ECU connector
(1) Disconnect the connector, connect the ASC check harness 

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

(2) Measure the voltage between the terminal No. 1 and the 

body ground.

OK: System voltage

Q: Is the check result normal?

YES : Go to Step 10.
NO :  Go to Step 8.

STEP 8. Fusible link check: Check the fusible link No.26.
Visually check for open circuit in the fusible link No.26.
Q: Is the check result normal?

YES : An open circuit may be present in the pump motor 

power supply circuit. Repair the wiring harness 
between A-05 ASC-ECU connector terminal No. 1 
and the fusible link No. 26.

NO :  Go to Step 9.

STEP 9. Wiring harness check between A-05 ASC-ECU 
connector and fusible link No. 26.
(1) Disconnect ASC-ECU connector A-05.
(2) Remove fusible link No. 26.
(3) Check the continuity (short to ground) between A-05 

ASC-ECU connector terminal No. 1 and the ground.

OK: No continuity

Q: Is the check result normal?

YES : Replace the fusible link No.26.
NO :  Short circuit may be present in the power supply 

circuit. Repair the wiring harness between A-05 
ASC-ECU connector terminal No. 1 and fusible link 
No. 26.

AC400817CP

ASC-ECU

MB991997

A-05 ASC-ECU 
harness connector

Check harness