Mitsubishi Lancer (4A9 engine). Manual - part 72

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-141

STEP 7. Check the part number of ASC-ECU
Check the part number of ASC-ECU.

Q: Is the check result normal?

YES : 

Go to Step 8.

NO : 

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

P.35C-185

), and then 

go to Step 9.

STEP 8. Check whether the diagnosis code is 
reset.
Erase the diagnosis code.

Q: Is diagnosis code No.U1417 set?

YES : 

Replace the hydraulic unit (integrated with 

ASC-ECU) (Refer to 

P.35C-185

), and then 

go to Step 9.

NO : 

The trouble can be an intermittent 
malfunction (Refer to GROUP 00 

− How to 

Use Troubleshooting/How to Cope with 
Intermittent Malfunctions ).

STEP 9. Check whether the diagnosis code is 
reset.
Erase the diagnosis code.

Q: Is diagnosis code No.U1417 set?

YES : 

Return to Step 1.

NO : 

This diagnosis is complete.

TROUBLE SYMPTOM CHART

M1355006900941

CAUTION

• ABS may operate in the following conditions without hard braking: Low mu road surface, high-

speed turn, and bumpy road surface. When asking the customers, confirm that they have/have not 
encountered ABS operation in corresponding conditions.

• During ABS operation, the brake pedal is pulled forward gradually, and the noise occurs at the 

same time. This is because the brake line pressure varies intermittently to prevent the wheel lock, 
and not a system malfunction.

CAUTION

During diagnosis, a diagnosis code associated with other system may be set when the ignition switch 
is turned on with connector(s) disconnected. On completion, confirm all systems for diagnosis 
code(s). If diagnosis code(s) are set, erase them all.

Trouble symptom

Inspection 
procedure 
number

Reference 
page

M.U.T.-III cannot communicate with 
the ABS/ASC system.

M.U.T.-III cannot communicate with 
all systems.

−

Refer to 
GROUP 54C 
− 
Troubleshooti
ng .

M.U.T.-III cannot communicate only 
with ASC-ECU.

1

P.35C-142

ASC OFF display or lamp flashes at a rate of 2Hz.

2

P.35C-142

Brake warning lamp stays ON with the parking brake lever released (ABS 
warning lamp is OFF).

3

P.35C-144

ABS warning lamp does not illuminate when ignition switch is turned to the 
ON position (Engine stopped).

4

P.35C-147

Brake warning lamp does not illuminate when the ignition switch is turned to 
ON position (Engine stopped).

5

P.35C-149

ABS warning lamp stays ON after the engine is started.

6

P.35C-150

ASC warning display stays ON after the engine is started.

7

P.35C-151

ASC OFF display or lamp stays ON after the engine is started.

8

P.35C-152

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-142

SYMPTOM PROCEDURES

Inspection Procedure 1: M.U.T.-III communication with ABS/ASC system is impossible.

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.

• If the power is supplied with the earth circuit 

of CAN communication device open circuited, 
an electric potential abnormality may occur to 
the CAN bus lines.

• 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
When M.U.T.-III cannot communicate with the ABS/
ASC system, the CAN bus lines, ASC-ECU power 
supply circuit system, earth, or ASC-ECU may be 
faulty.

PROBABLE CAUSES

• Damaged wiring harness and connectors

• ASC-ECU malfunction

• Wrong routing of M.U.T.-III harness

• Abnormality in battery or alternator

• Abnormality in power supply voltage to ASC-ECU

• ECU malfunction of other system

M.U.T.-III CAN bus diagnosis
Use M.U.T.-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES : 

Check the power supply circuit, and repair if 

necessary (Refer to 

P.35C-159

).

NO : 

Repair the CAN bus lines (Refer to GROUP 
54C 

− CAN Bus Diagnostics Table ).

Inspection Procedure 2: ASC OFF display or lamp flashes at a rate of 2Hz.

OPERATION
When the ASC OFF display or lamp flashes at a rate 
of 2 Hz, the TCL control (brake control only) is pro-

hibited.

The stability control/TCL system cannot be disabled when ASC OFF switch is 
pressed for 3 seconds or more to turn the system OFF.

9

P.35C-155

Abnormality in brake operation

10

P.35C-157

Stability control/TCL does not work.

11

P.35C-158

ASC-ECU power supply circuit system

12

P.35C-159

Steering wheel sensor power supply circuit system

13

P.35C-167

ABS/stability control/TCL operates too frequently.

14

P.35C-169

ESS inoperative or improper operative.

15

P.35C-171

The initial check sound of hydraulic unit is loud.

16

P.35C-172

Trouble symptom

Inspection 
procedure 
number

Reference 
page

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-143

COMMENTS ON TROUBLE SYMPTOM
This operation is performed for the following reasons 
and is not a malfunction.

• ASC-ECU calculates the estimated temperature 

of the brake pad. In general, as the brake pad 
temperature increases, the coefficient of friction 
for the brake pad becomes smaller, resulting in 
the reduced braking force. When the estimated 
temperature of the brake pad reaches the speci-
fied value or more, ASC-ECU flashes the ASC 

OFF display or lamp at a rate of 2 Hz to warn the 
driver that the brake controllability by TCL is 
decreased by the reduced braking force. Conse-
quently, ASC-ECU prohibits the TCL control 
(brake control only) until it determines that the 
estimated temperature of the brake pad is nor-
mal.

PROBABLE CAUSES

• Overheat of brake pad

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-144

Inspection Procedure 3: Brake warning lamp stays ON with the parking brake lever released (ABS 
warning lamp is OFF).

ETACS-
ECU

INTERFACE 
CIRCUIT

CAN DRIVE 
CIRCUIT

CAN 
TRANSCEIVER 
CIRCUIT

INTERFACE 
CIRCUIT

INTERFACE 
CIRCUIT

LED DRIVE 
CIRCUIT

CPU

LCD

COMBINATION METER

Brake Warning Lamp Circuit

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

BRAKE 
FLUID 
LEVEL 
SWITCH

PARKING 
BRAKE 
SWITCH

ACB02564