Mitsubishi Lancer Evolution X. Manual - part 197

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-253

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.

.

SYSTEM OPERATION

• The ETACS-ECU terminal No. 15 is grounded when the 

ASC OFF switch is pressed. The ON/OFF status of ASC 
OFF switch is sent from ETACS-ECU to ASC-ECU via CAN 
bus line.

• When the ASC OFF switch is pressed shortly, the ASC sys-

tem is turned OFF.

• When the ASC OFF switch is pressed and held for 15 sec-

onds or more, the ASC OFF indicator light is turned off, and 
the ASC system is turned ON.

.

TECHNICAL DESCRIPTION (COMMENT)

In the case of this trouble symptom, there may be an open and 
short circuit to the ASC OFF switch circuit.

.

PROBABLE CAUSES

• Damaged wiring harness and connectors
• ASC OFF switch malfunction
• ETACS-ECU malfunction
• Combination meter 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

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 2.
NO :  Repair the CAN bus lines. (Refer to GROUP 54C − 

Troubleshooting 

P.54C-15

.) After repairing the CAN 

bus line, go to Step 8.

STEP 2. ASC OFF switch check
Refer to 

P.35C-297

.

Q: Is the check result normal?

YES : Go to Step 3.
NO :  Replace the ASC OFF switch. (Refer to 

P.35C-296

.) 

Then, go to Step 8.

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-254

STEP 3. Connector check: C-313 ETACS-ECU connector, 
C-42 intermediate connector, C-135 ASC OFF switch 
connector
Q: Is the check result normal?

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

STEP 4. Wiring harness check between C-313 ETACS-ECU 
connector terminal No. 15 and C-135 ASC OFF switch 
connector terminal No. 1

• Check the power supply circuit for open and short circuit.

Q: Is the check result normal?

YES : Go to Step 5.
NO :  Repair the wiring harness between C-313 

ETACS-ECU connector terminal No. 15 and C-135 
ASC OFF switch connector terminal No. 1.

STEP 5. Wiring harness check between C-135 ASC OFF 
switch connector terminal No. 2 and the body ground

• Open circuit check of the ground circuit

Q: Is the check result normal?

YES : Go to Step 6.
NO :  Repair the wiring harness between C-135 ASC OFF 

switch connector terminal No. 2 and the body ground.

STEP 6. Retest the system.
Q: Does ASC turn ON and OFF normally using the ASC 

OFF switch?
YES : Intermittent malfunction. (Refer to GROUP 00 − How 

to Cope with Intermittent Malfunction 

P.00-15

.)

NO :  Replace the ETACS-ECU. (Refer to GROUP 54A − 

ETACS-ECU 

P.54A-742

.) Then, go to Step 7.

STEP 7. Retest the system.
Q: Does ASC turn ON and OFF normally using the ASC 

OFF switch?
YES : The procedure is complete.
NO :  Replace the combination meter. (Refer to GROUP 

54A − Combination Meter 

P.54A-110

.) Then, go to 

Step 8.

STEP 8. Retest the system.
Q: Does ASC turn ON and OFF normally using the ASC 

OFF switch?
YES : The procedure is complete.
NO :  Return to Step 1.

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-255

Inspection Procedure 9: Abnormality in brake operation

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-287

, 

P.35C-289

, 

P.35C-294

, and 

P.35C-295

.)

.

TECHNICAL DESCRIPTION (COMMENT)

Although it is difficult to determine the trouble cause since it 
depends on the running status and road surface condition, a 
malfunction of hydraulic circuit may be present if no diagnostic 
trouble code is detected.

.

PROBABLE CAUSES

• Malfunction of hydraulic unit (integrated with ABS-ECU)
• Malfunction of hydraulic circuit
• Malfunction of brake assembly
• Malfunction of brake booster
• Malfunction of master cylinder assembly

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

STEP 1. Check the DTC.
Using scan tool, check the diagnostic trouble code for ASC sys-
tem. (Refer to 

P.35C-22

.)

Q: Is the check result normal?

YES : Go to Step 2.
NO :  Carry out the diagnosis for DTC. (Refer to 

P.35C-22

.)

STEP 2. Hydraulic unit (integrated with ASC-ECU) check
Check that the brake tube is correctly mounted to the hydraulic 
unit (integrated with ASC-ECU). (Refer to 

P.35C-284

.)

Q: Is the check result normal?

YES : Go to Step 3.
NO :  Connect the brake tubes correctly, and repair or 

replace the external brake lines of the hydraulic unit 
(integrated with ASC-ECU).

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-256

STEP 3. Brake operation check
Perform the following checks.

• Brake pedal check (Refer to GROUP 35A − On-vehicle Ser-

vice, Brake Pedal Check 

P.35A-12

.)

• Brake booster check (Refer to GROUP 35A − On-vehicle 

Service, Brake Booster Operation Check 

P.35A-15

.)

• Check valve check (Refer to GROUP 35A − On-vehicle Ser-

vice, Check Valve Operation Check 

P.35A-16

.)

Q: Can any fault be found with the brake operation?

YES : Check the brake-related parts, and repair if 

necessary. Then, go to Step 4.

NO :  Go to Step 4.

STEP 4. Hydraulic unit check
Perform the following actuator tests. (Refer to 

P.35C-278

.)

• Item 01: FL wheel ABS drive
• Item 02: FR wheel ABS drive
• Item 03: RL wheel ABS drive
• Item 04: RR wheel ABS drive
• Item 05: FL wheel TCL drive
• Item 06: FR wheel TCL drive
• Item 07: RL wheel TCL drive
• Item 08: RR wheel TCL drive

Q: Is the check result normal?

YES : The procedure is complete.
NO :  Replace the hydraulic unit (incorporates in 

ASC-ECU).(Refer to 

P.35C-298

.)

Inspection Procedure 10: Skid control/TCL does not operate.

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-287

, 

P.35C-289

, 

P.35C-294

, and 

P.35C-295

.)

.

TECHNICAL DESCRIPTION (COMMENT)

In case of this trouble symptom, the operation of skid con-
trol/TCL system may be disabled. In this case, a diagnostic 
trouble code may be set by the skid control/TCL system using 
the scan tool.

.