Mitsubishi Lancer (4A9 engine). Manual - part 76

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-157

Inspection Procedure 10: Abnormality in brake operation

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

).

COMMENTS ON TROUBLE SYMPTOM
Although the cause of the trouble cannot be clearly 
resolved since it depends on the running status and 
road surface condition, the malfunction of the 
hydraulic circuit may occur if any diagnosis code is 
not detected.

PROBABLE CAUSES

• Hydraulic unit (Integrated with ASC-ECU) mal-

function

• Malfunction of hydraulic circuit

• Malfunction of brake assembly

• Malfunction of brake booster

• Malfunction of master cylinder assembly

DIAGNOSIS PROCEDURE

STEP 1. Diagnosis code check
Use M.U.T.-III to check the diagnosis code for the 
ASC system. (Refer to 

P.35C-16

.)

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Troubleshoot for the relevant diagnosis 
code (Refer to 

P.35C-16

).

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

P.35C-179

).

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Connect the brake tubes correctly, repair the 
external brake lines, or replace the hydraulic 
unit (integrated with ASC-ECU) (Refer to 

P.35C-185

).

STEP 3. Brake operation check
Perform the following checks.

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

vehicle Service/Brake Pedal Check and Adjust-
ment .)

• Brake booster check (Refer to GROUP 35A − 

On-vehicle Service/Brake Booster Operating 
Check .)

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

vehicle Service/Check Valve Operation Check .)

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-

175

).

• Item No.01: FL wheel ABS drive

• Item No.02: FR wheel ABS drive

• Item No.03: RL wheel ABS drive

• Item No.04: RR wheel ABS drive

• Item No.05: FL wheel TCL drive

• Item No.06: FR wheel TCL drive

• Item No.07: RL wheel TCL drive

• Item No.08: RR wheel TCL drive

Q: Is the check result normal?

YES : 

This diagnosis is complete.

NO : 

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

P.35C-185

).

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-158

Inspection Procedure 11: ASC does not operate or faulty ASC operate.

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

).

COMMENTS ON TROUBLE SYMPTOM
In case of this trouble symptom, the stability control/
TCL system operation may be disabled. Diagnosis 
code may be set by the stability control/TCL system 
using M.U.T.-III.

PROBABLE CAUSES

• Low battery output

• Wiring harness or connector failure of CAN bus 

line

• ASC-ECU malfunction

• Engine coding data problem

DIAGNOSIS PROCEDURE

STEP 1. Diagnosis code check
Use M.U.T.-III to check the diagnosis code for the 
ASC system. (Refer to 

P.35C-16

.)

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Carry out the diagnosis for the diagnosis 
code. (Refer to 

P.35C-16

.)

STEP 2. Engine ECU coding data check
Using M.U.T.-III, check if any abnormality is present 
to the coding data below which are stored in the 
engine-ECU (Refer to GROUP 00 

− Precautions 

before Service/Coding List ).

A.S.C.

OK: Available

Q: Is the check result normal?

YES : 

Go to Step 4.

NO : 

Go to Step 3.

STEP 3. Engine ECU coding data check
Perform the variant coding to the Engine ECU.

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Replace the engine ECU (Refer to GROUP 
13A 

− Engine-ECU  <4A9>, GROUP 13B − 

Engine-ECU  <4B1>, GROUP 13F 

− 

Engine-ECU  <4J1> or GROUP 13C 

− 

Engine-ECU  <4N1>). Then go to Step 5.

STEP 4. 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-179

.)

Q: Is the check result normal?

YES : 

Replace the hydraulic unit (integrated with 

ASC-ECU).(Refer to 

P.35C-179

.) Then go 

to Step 5.

NO : 

Connect the brake tubes correctly, and 
repair or replace the external brake lines of 
the hydraulic unit (integrated with ASC-
ECU).

STEP 5. Operation check

Q: Does stability control/TCL operate normally?

YES : 

This diagnosis is complete.

NO : 

Check the brake system related 
components other than the stability control/
TCL system.

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-159

Inspection Procedure 12: ASC-ECU power supply circuit system

Solenoid Valve, Motor and ASC-ECU Power Source Circuit

SOLENOID 
VALVE 
POWER 
SOURCE

MOTOR 
POWER 
SOURCE

ETACS-
ECU

ASC-ECU

POWER 
SOURCE

POWER 
SOURCE

IG1 
RELAY

IGNITION SWITCH

<PETROL>

FUSIBLE 
LINK

34

<DIESEL>

FUSIBLE 
LINK

44

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

FUSIBLE 
LINK

26

FUSIBLE 
LINK

27

ACB02568

AC612691

AO

Connector: A-58 <LHD>

A-58 (B)

AC701238 AF

Connector: A-58 <RHD>

A-58 (B)

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-160

CAUTION

• When the ASC-ECU power supply voltage 

becomes 9.7 

± 0.3 V or less, the ABS warning 

lamp, ASC warning display, and ASC OFF dis-
play illuminate, and the ABS, stability control, 
and TCL controls are prohibited.

• If the battery terminal is not tightened prop-

erly, a dump surge may occur and the power 
supply voltage may become abnormally high 
for a short time.

• 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 contains the power supply circuit (ter-

minal No.32) for the solenoid valve. The solenoid 
valve is energised by the valve relay, which is 
incorporated in ASC-ECU.

• ASC-ECU contains the power supply circuit (ter-

minal No.2) for ASC-ECU. The power is supplied 
from the fusible link No.34 <PETROL> or fusible 
link No.44 <DIESEL> through the multi-purpose 
fuse No.17.

• ASC-ECU contains the power supply circuit (ter-

minal No. 8) for ASC-ECU. When the ignition 
switch (IG1) is turned ON, the voltage is applied 
to the relay incorporated in ETACS-ECU to turn 
ON the relay, and the power is supplied from the 
fusible link No. 34 <PETROL> or fusible link 
No.44 <DIESEL> through multi-purpose fuse No. 
12.

• ASC-ECU contains the power supply circuit (ter-

minal No.1) for the pump motor. The pump motor 
is energised by the motor switch, which is incor-
porated in ASC-ECU.

• When malfunction occurs in ASC-ECU power 

supply, the communication with M.U.T.-III 
becomes unavailable.

PROBABLE CAUSES

• Damaged wiring harness and connectors

• Fuse and fusible link malfunction

• Improper tightening of battery terminal

• Improper tightening of earth bolt

• Battery failure

• Charging system failed

• ASC-ECU malfunction

DIAGNOSIS PROCEDURE

STEP 1. Battery check
Refer to GROUP 54A 

− Battery Test .

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 

− On−vehicle Service/Alternator 

Output Line Voltage Drop Test .

Q: Is the charging system in good condition?

YES : 

Go to Step 3.

NO : 

Repair or replace the charging system 
component(s).