Mitsubishi Evolution X. Manual - part 779

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-123

PROBABLE CAUSES

Current trouble

• Fusible link malfunction

• Damaged wiring harness and connectors

• Abnormality in battery or generator

• ASC-ECU malfunction

Past trouble

• Perform the diagnosis with a particular emphasis on the wir-

ing harness and connector failures in the ASC-ECU motor 
power supply circuit (A-05 ASC-ECU connector terminal 
No. 1) and in the ground circuit (A-05 ASC-ECU connector 
terminal No. 16 and No.47). For diagnosis procedures, refer 
to How to Treat Past Trouble (GROUP 00 

− How to Use 

Troubleshooting/Inspection Service Points 

P.00-16

).

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-14

.) After repairing the CAN 

bus line, go to Step 2.

STEP 2. DTC recheck after repairing the CAN bus line
Q: Is DTC C1073 set?

YES : Go to Step 3.
NO :  The procedure is complete.

STEP 3. Fusible link check: Check the fusible link No. 26.
Q: Is the check result normal?

YES : Go to Step 4.
NO :  Replace the fusible link No.26.

STEP 4. Battery check
Refer to GROUP 54A 

− Battery Test 

P.54A-9

.

Q: Is the battery in good condition?

YES : Go to Step 5.
NO :  Charge or replace the battery.

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-124

STEP 5. 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 6.
NO :  Repair or replace the charging system component(s).

STEP 6. Voltage measurement at the 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 8.
NO :  Go to Step 7.

STEP 7. Connector check: A-05 ASC-ECU connector
Q: Is the check result normal?

YES : An open or short 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  :  Repair the defective connector.

AC400817CP

ASC-ECU

MB991997

A-05 ASC-ECU 
harness connector

Check harness

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-125

STEP 8. Resistance 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 resistance between the terminal No. 16 and 

the body ground as well as between the terminal No. 47 
and the body ground.

OK: Continuity exists (2 

Ω or less)

Q: Is the check result normal?

YES : Go to Step 10.
NO :  Go to Step 9.

STEP 9. Connector check: A-05 ASC-ECU connector
Q: Is the check result normal?

YES : An open circuit may be present in the ground circuit. 

Repair the wiring harness between A-05 ASC-ECU 
connector terminal No. 16 and the ground as well as 
between A-05 ASC-ECU connector terminal No. 47 
and the ground.

NO  :  Repair the defective connector.

STEP 10. Check whether the DTC is reset.
(1) Erase the diagnostic trouble code.
(2) Drive the vehicle at 12mph (20 km/h) or more.

NOTE: The ABS warning light does not turn OFF in some 
cases unless the vehicle runs at 12mph (20 km/h) or higher.

Q: Is DTC C1073 set?

YES : Replace the hydraulic unit (incorporates in 

ASC-ECU).(Refer to 

P.35C-272

.) Then go to Step 11.

NO :  Intermittent malfunction. (Refer to GROUP 00 

− How 

to Cope with Intermittent Malfunction 

P.00-15

.)

AC400817CO

ASC-ECU

MB991997

A-05 ASC-ECU 
harness connector

Check harness

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-126

STEP 11. Check whether the DTC is reset.
(1) Erase the diagnostic trouble code.
(2) Drive the vehicle at 12mph (20 km/h) or more.

NOTE: The ABS warning light does not turn OFF in some 
cases unless the vehicle runs at 12mph (20 km/h) or higher.

Q: Is DTC C1073 set?

YES : Return to Step 1.
NO :  This diagnosis is complete.

DTC C2116: Abnormality in power supply voltage in pump motor

CAUTION

• 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

.)

.

CIRCUIT OPERATION

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

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

• The pump motor switch in ASC-ECU is turned off at all 

times unless during the motor solenoid valve check per-
formed when the vehicle is started.

• ASC-ECU activates the pump motor by turning on the ECU 

built-in pump motor switch.

.

AC708948

Connector: A-05

A-05 (B)

AB