Mitsubishi Lancer (4A9 engine). Manual - part 62

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-101

STEP 8. Connector check: C-304 ETACS-ECU 
connector, C-312 ETACS-ECU connector, C-24 
stop lamp switch connector, C-31 Intermediate 
connector, D-12 Intermediate connector, D-17 
Intermediate connector, F-28 Intermediate 
connector <LANCER>, F-39 Intermediate 
connector <LANCER SPORTBACK>, F-08 rear 
combination lamp (stop: RH) connector, F-23 rear 
combination lamp (stop: LH) connector, F-11 
highmounted stop lamp connector

Q: Is the check result normal?

YES : 

Go to Step 9.

NO : 

Repair the damaged connector, and then 
replace fuse No.2. Then go to Step 19.

STEP 9. Resistance measurement at C-24 stop 
lamp switch connector
(1) Disconnect C-24 stop lamp switch connector, and 

measure at the wiring harness side.

(2) Disconnect C-312 ETACS-ECU connector and C-

30 joint connector.

(3) Measure the resistance between the terminal 

No.1 and the body earth.

OK: No continuity

Q: Is the check result normal?

YES : 

Go to Step 10.

NO : 

A short circuit may be present in the wiring 
harness between C-24 stop lamp switch 
connector terminal No.1 and F-08 rear 
combination lamp (stop: RH) connector 
terminal No.4 <LANCER>, No.1 <LANCER 
SPORTBACK>, F-23 rear combination lamp 
(stop: LH) connector terminal No.4 
<LANCER>, No.1 <LANCER 
SPORTBACK>, F-11 highmounted stop 
lamp connector terminal No.1 <LANCER>, 
No.2 <LANCER SPORTBACK> or between 
C-312 ETACS-ECU connector terminal 
No.16 and C-24 stop lamp switch connector 
terminal No.1. Repair the wiring harness if 
necessary, and then replace fuse No.2. 
Then go to Step 19.

STEP 10. Resistance measurement at C-24 stop 
lamp switch connector
(1) Disconnect C-24 stop lamp switch connector, and 

measure at the wiring harness side.

(2) Disconnect C-304 ETACS-ECU connector.
(3) Measure the resistance between the terminal 

No.2 and the body earth.

OK: No continuity

Q: Is the check result normal?

YES : 

Go to Step 11.

NO : 

A short circuit may be present in the wiring 
harness between C-304 ETACS-ECU 
connector terminal No.1 and C-24 stop lamp 
switch connector terminal No.2. Repair the 
wiring harness if necessary, and then 
replace fuse No.2. Then go to Step 19.

STEP 11. Connector check: C-304 ETACS-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 12.

NO : 

Repair the damaged connector.

STEP 12. Measure the voltage at the C-304 
ETACS-ECU connector.

CAUTION

Measure while the brake pedal is not depressed.
Measure the voltage between terminal No. 1 and the 
body earth by backprobing.

OK: Approximately system voltage

Q: Is the check result normal?

YES : 

Go to Step 13.

NO : 

Replace the ETACS-ECU (Refer to GROUP 
54A 

− ETACS-ECU ). Then go to Step 19.

STEP 13. Connector check: C-24 Stop lamp 
switch connector

Q: Is the check result normal?

YES : 

Go to Step 14.

NO : 

Repair the damaged connector.

STEP 14. Measure the voltage at C-24 stop lamp 
switch connector.
(1) Disconnect C-24 stop lamp switch connector, and 

measure the voltage at harness connector side.

(2) Measure the voltage between the terminal No.2 

and the body earth.

OK: Approximately system voltage

Q: Is the check result normal?

YES : 

Go to Step 15.

NO : 

An open circuit may be present in the wiring 
harness between C-304 ETACS-ECU 
connector terminal No. 1 and C-24 stop 
lamp switch connector terminal No. 2. 
Repair the wiring harness.

STEP 15. Connector check: C-312 ETACS-ECU 
connector

Q: Is the check result normal?

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-102

YES : 

Go to Step 16.

NO : 

Repair the damaged connector.

STEP 16. Measure the voltage at the C-312 
ETACS-ECU connector.
(1) Measure by backprobing without disconnecting 

the connector.

(2) Measure the voltage between the terminal No.16 

and the body earth.

OK:

When the brake pedal is released: 0 V - 5V 

(pulse)

When the brake pedal is depressed: 

Approximately system voltage

Q: Is the check result normal?

YES : 

Go to Step 18.

NO : 

Go to Step 17.

STEP 17. Check the wiring harness between C-
312 ETACS-ECU connector terminal No.16 and C-
24 stop lamp switch connector terminal No.1

• Check the signal line for open circuit.

Q: Is the check result normal?

YES : 

Replace the ETACS-ECU.

NO : 

Repair the wiring harness.

STEP 18. Diagnosis code recheck
Erase the diagnosis code.

Q: Is diagnosis code No.C1000 set?

YES : 

Replace the hydraulic unit (integrated with 

ASC-ECU) (Refer to 

P.35C-185

). Then go 

to Step 19.

NO : 

Intermittent malfunction (Refer to GROUP 
00 

− How to Use Troubleshooting/How to 

Cope with Intermittent Malfunctions .)

STEP 19. Diagnosis code recheck
Erase the diagnosis code.

Q: Is diagnosis code No.C1000 set?

YES : 

Return to Step 1.

NO : 

This diagnosis is complete.

Code No.C123B: Prolonged operation of ASC

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.

• Do not drop or shock the G and yaw rate sen-

sor.

• When the G and yaw rate sensor is replaced, 

always carry out calibration to make ASC-
ECU learn the neutral point (Refer to 

P.35C-

182

).

• 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 controls ASC by calculating the data sent 
from the wheel speed sensor, the steering wheel 
sensor, and the G and yaw rate sensor.

DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set when ASC operates for a 
prolonged period.
NOTE: This diagnosis code may be set when the 
vehicle runs on a slippery or rough road.

PROBABLE CAUSES

• Steering wheel sensor malfunction

• G and yaw rate sensor malfunction

• Improper installation of steering wheel sensor, or 

G and yaw rate sensor

• ASC-ECU malfunction

• Different steering wheel

• Wheel alignment not performed

DIAGNOSIS PROCEDURE

STEP 1. Using M.U.T.-III, diagnose the CAN bus 
lines.
Using M.U.T.-III, diagnose the CAN bus lines.

Q: Is the check result normal?

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-103

YES : 

Go to Step 3.

NO : 

Repair the CAN bus lines (Refer to GROUP 
54C 

− CAN Bus Diagnostics Table ). After 

repairing the CAN bus line, go to Step 2.

STEP 2. Diagnosis code recheck after repairing 
the CAN bus line

Q: Is diagnosis code No.C123B set?

YES : 

Go to Step 3.

NO : 

This diagnosis is complete.

STEP 3. M.U.T.-III diagnosis code
Check that diagnosis codes No.C100A, C1015, 
C1020, C102B, C1011, C101C, C1027, C1032, 
C1014, C101F, C102A, C1035, C1041, C1042, 
C1043, C1044, C1219, C2205, C123C, and C2204 
are also set.

Q: Are diagnosis codes No.C100A, C1015, C1020, 

C102B, C1011, C101C, C1027, C1032, C1014, 
C101F, C102A, C1035, C1041, C1042, C1043, C1044, 
C1219, C2205, C123C, and C2204 also set?
YES : 

Carry out the diagnosis for the diagnosis 

code that is set (Refer to 

P.35C-16

). Then 

go to Step 10.

NO : 

Go to Step 4.

STEP 4. Check of G and yaw rate sensor 
installation status
Check that the G and yaw rate sensor is installed 
correctly.

Q: Is the check result normal?

YES : 

After checking the G and yaw rate sensor, 

perform the calibration of the G and yaw 
rate sensor to make ASC-ECU relearn the 
neutral point (Refer to 

P.35C-182

). Then go 

to Step 5.

NO : 

Reinstall the G and yaw rate sensor 
correctly (Refer to 

P.35C-189

). Then go to 

Step 10.

STEP 5. M.U.T.-III service data
Check the following data list (Refer to 

P.35C-172

).

• Item 08: Lateral G sensor

• Item 09: G sensor

• Item 12: Yaw rate sensor

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Replace the G and yaw rate sensor (Refer 
to 

P.35C-189

). Then go to Step 10.

STEP 6. Check of steering wheel sensor 
installation status
Check that the steering wheel sensor is installed cor-
rectly.

Q: Is the check result normal?

YES : 

Go to Step 7.

NO : 

Install the steering wheel sensor correctly 
(Refer to 

P.35C-190

). Then go to Step 7.

STEP 7. Wheel alignment check
Refer to GROUP 33 

− On-vehicles service/Front 

Wheel Alignment Check and Adjustment .

Q: Is the check result normal?

YES : 

After checking the wheel alignment, perform 

the calibration of steering wheel sensor to 
make ASC-ECU relearn the neutral point 
(Refer to 

P.35C-183

). Then go to Step 8.

NO : 

After adjusting the wheel alignment, perform 
the calibration of steering wheel sensor to 
make ASC-ECU relearn the neutral point 
(Refer to 

P.35C-183

). Then go to Step 8.

STEP 8. M.U.T.-III service data
Check the following data list (Refer to 

P.35C-172

).

• Item 11: Steering angle

Q: Is the check result normal?

YES : 

Go to Step 9.

NO : 

Replace the steering wheel sensor (Refer to 

P.35C-190

). Then go to Step 10.

STEP 9. Check whether the diagnosis code is 
reset.
(1) Erase the diagnosis code.
(2) Drive the vehicle at 20 km/h or higher.

Q: Does ASC unnecessary activation occur or is the 

diagnosis code No. C123B set? 
YES : 

Replace the hydraulic unit (integrated with 

ASC-ECU) (Refer to 

P.35C-185

). Then go 

to Step 10.

NO : 

Intermittent malfunction (Refer to GROUP 
00 

− How to Use Troubleshooting/How to 

Cope with Intermittent Malfunctions ).

STEP 10. Check whether the diagnosis code is 
reset.
(1) Erase the diagnosis code.
(2) Drive the vehicle at 20 km/h or higher.

Q: Does ASC unnecessary activation occur or is the 

diagnosis code No. C123B set? 
YES : 

Return to Step 1.

NO : 

The procedure is complete.

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-104

Code No. C2200 Abnormality in ASC-ECU

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 controls ASC by calculating the data sent 
from the wheel speed sensor, the steering wheel 
sensor, and the G and yaw rate sensor.

DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set when ASC-ECU has mal-
function.

PROBABLE CAUSES
ASC-ECU malfunction

DIAGNOSIS PROCEDURE

STEP 1. 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 : 

Go to Step 2.

NO : 

Repair the CAN bus lines (Refer to GROUP 
54C 

− CAN Bus Diagnostics Table ). On 

completion, go to Step 2.

STEP 2. Diagnosis code recheck after resetting 
CAN bus lines
Erase the diagnosis code.

Q: Is diagnosis code No.C2200 set?

YES : 

Replace the hydraulic unit (integrated with 

ASC-ECU) (Refer to 

P.35C-185

). Then go 

to Step 3.

NO : 

Intermittent malfunction (Refer to GROUP 
00 

− How to Use Troubleshooting/How to 

Cope with Intermittent Malfunctions ).

STEP 3. Diagnosis code recheck after resetting 
CAN bus lines
Erase the diagnosis code.

Q: Is diagnosis code No.C2200 set?

YES : 

Return to Step 1.

NO : 

This diagnosis is complete.

Code No. C2101 Abnormality in battery voltage (high voltage)

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
The ASC-ECU is energized by the valve power sup-
ply circuit (terminal No.32). When the power is sup-

plied from the ignition switch (IG1) to the IG1 relay in 
ETACS-ECU, IG1 relay is turned on. At this time, the 
valve power supply circuit (terminal No.2) energizes 
the ASC-ECU.

DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set when the ASC-ECU power 
supply voltage is more than 18.0 

± 1.0 V.

PROBABLE CAUSES

• Battery failure

• ASC-ECU malfunction

• Charging system failed

• Battery terminal looseness