Mitsubishi Lancer (4A9 engine). Manual - part 75

AC701122 DA

Connector: C-135 <RHD>

AC607219

AI

Connector: C-313 <LHD>

C-313 (BR)

AC607229AI

Connector: C-313 <RHD>

C-313 (BR)

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-153

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

• ASC-ECU sends the illumination request signal 

of ASC OFF display to the combination meter 
through ETACS-ECU via CAN communication.

• By the operation of ASC OFF switch, the ASC 

OFF display illuminates when the ASC function is 
stopped.

• When the ASC OFF switch is pressed for 3 sec-

onds or more, the ASC system turns OFF.

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

onds or more, the ASC is kept in ON state and 
the system cannot be turned OFF until the igni-
tion switch is turned to the ON position next time.

COMMENTS ON TROUBLE SYMPTOM
This may be caused by faults in the CAN bus line, 
ETACS-ECU, combination meter or ASC-ECU.

PROBABLE CAUSES

• Damaged wiring harness and connectors

• Malfunction of ETACS-ECU

• Combination meter malfunction

• ASC-ECU malfunction

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use M.U.T.-III to 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 

− CAN Bus Diagnostics Table ). Then 

go to Step 9.

STEP 2. M.U.T.-III diagnosis code
Use M.U.T.-III to check the diagnosis code for the 
ASC system.

Q: Is the diagnosis code set?

YES : 

Carry out the diagnosis for the diagnosis 

code chart (Refer to 

P.35C-16

).

NO : 

Go to Step 3.

STEP 3. ASC OFF switch check
Refer to 

P.35C-185

.

Q: Is the check result normal?

YES : 

Go to Step 4.

NO : 

Replace ASC OFF switch (Refer to 

P.35C-

184

). Then go to Step 9.

STEP 4. Connector check: C-313 ETACS-ECU 
connector, C-27 intermediate connector, C-135 
ASC OFF switch connector

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Repair the damaged connector.

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-154

STEP 5. Wiring harness check between C-313 
ETACS-ECU connector terminal No. 15 and C-135 
ASC OFF switch connector terminal No. 1

• Check the signal circuit for short circuit.

Q: Is the check result normal?

YES : 

Go to Step 6.

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 6. M.U.T.-III diagnosis code for other 
systems
Using M.U.T.-III, check that diagnosis code No. 
U0141 is set by the combination meter system.

Q: Is the diagnosis code set?

YES : 

Diagnose the combination meter (Refer to 

GROUP 54A 

− Combination Meter/

Diagnosis Code ). Then go to Step 9.

NO : 

Go to Step 7.

STEP 7. M.U.T.-III diagnosis code for other 
systems
Using M.U.T.-III, check that diagnosis code No. 
U0121 is set by the ETACS system.

Q: Is the diagnosis code set?

YES : 

Perform troubleshooting on ETACS-ECU 

(Refer to GROUP 54A 

− ETACS/Diagnosis 

Code ). Then go to Step 8.

NO : 

Go to Step 8.

STEP 8. Retest the system.

Q: Does ASC OFF display turn ON and OFF normally?

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use Troubleshooting/How to 

Cope with Intermittent Malfunctions .)

NO : 

Replace the hydraulic unit (integrated with 
ASC-ECU) (Refer to 

P.35C-185

). Then go 

to Step 9.

STEP 9. Retest the system.

Q: Does ASC OFF display turn ON and OFF normally?

YES : 

This diagnosis is complete.

NO : 

Return to Step 1.

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-155

Inspection Procedure 9: The stability control/traction control function cannot be disabled when ASC 
OFF switch is pressed for 3 seconds or more to turn the system OFF.

ASC OFF Switch Circuit

ETACS-ECU

ASC
OFF
SWITCH

<RHD>

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

ACB02569

AC612705

Connectors: C-28, C-135 <LHD>

IT

C-28

C-135

AC612710

Connector: C-28 <RHD>

EB

AC701122 DA

Connector: C-135 <RHD>

AC607219

AI

Connector: C-313 <LHD>

C-313 (BR)

AC607229AI

Connector: C-313 <RHD>

C-313 (BR)

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-156

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.

OPERATION

• ETACS-ECU terminal No. 15 is earthed by press-

ing ASC OFF switch. The ON/OFF state of ASC 
OFF switch is transferred from ETACS-ECU to 
ASC-ECU via CAN bus line.

• When the ASC OFF switch is pressed for 3 sec-

onds or more, the ASC system turns OFF.

• When the ASC OFF switch is pressed and held 

for 15 seconds or more, ASC turns ON.

COMMENTS ON TROUBLE SYMPTOM
This may be caused by the open circuit or short cir-
cuit in the ASC OFF switch circuit.

PROBABLE CAUSES

• Damaged wiring harness and connectors

• ASC OFF switch malfunction 

• Malfunction of ETACS-ECU

DIAGNOSIS PROCEDURE

STEP 1. ASC OFF switch check
Refer to 

P.35C-185

.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Replace ASC OFF switch (Refer to 

P.35C-

184

). Then go to Step 6.

STEP 2. Connector check: C-313 ETACS-ECU 
connector, C-27 intermediate connector, C-135 
ASC OFF switch connector

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Repair the damaged connector.

STEP 3. Wiring harness check between C-313 
ETACS-ECU connector terminal No. 15 and C-135 
ASC OFF switch connector terminal No. 1

• Check the signal circuit for open and short circuit.

Q: Is the check result normal?

YES : 

Go to Step 4.

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 4. Wiring harness check between C-135 
ASC OFF switch connector terminal No. 2 and 
the body earth

• Check the earth wires for open circuit.

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Repair the wiring harness between C-135 
ASC OFF switch connector terminal No. 2 
and the body earth.

STEP 5. Retest the system.

Q: Does ASC turn ON and OFF normally using ASC 

OFF switch?
YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use Troubleshooting/How to 

Cope with Intermittent Malfunctions .)

NO : 

Replace the ETACS-ECU. (Refer to 
GROUP 54A 

− ETACS-ECU .) Then go to 

Step 6.

STEP 6. Retest the system.

Q: Does ASC turn ON and OFF normally using ASC 

OFF switch?
YES : 

This diagnosis is complete.

NO : 

Return to Step 1.