Mitsubishi Lancer (4A9 engine). Manual - part 66

AC612705

Connector: C-137 <LHD>

CG

C-137 (B)

AC701122

Connector: C-137 <RHD>

BL

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-117

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 supplies power to the G and yaw rate 

sensor at the terminal No.1.

• The G and yaw rate sensor outputs the signal to 

ASC-ECU via the special CAN bus lines.

DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set if any malfunction below is 
found:

Code No. C2114

• When the power supply voltage applied from 

ASC-ECU to the G and yaw rate sensor is not 
within the standard value range <low voltage (6.5 
± 0.5 V or less)>

Code No. C2115

• When the power supply voltage applied from 

ASC-ECU to the G and yaw rate sensor is not 
within the standard value range <high voltage 
(18.0 

± 1.0 V or more)>

PROBABLE CAUSES

• Damaged wiring harness and connectors

• G and yaw rate sensor malfunction

• 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. M.U.T.-III diagnosis code
Check that the diagnosis code No.U0125 is set in 
ASC-ECU.

Q: Is the diagnosis code No.U0125 set?

YES : 

Troubleshoot for the diagnosis code (Refer 

to 

P.35C-133

). Then go to Step 3.

NO : 

Go to Step 3.

STEP 3. Diagnosis code recheck

Q: Are the diagnosis codes No. C2114 or C2115 set?

YES : 

Go to Step 4.

NO : 

This diagnosis is complete.

STEP 4. M.U.T.-III data list
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 12.

NO : 

Go to Step 5.

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-118

STEP 5. Connector check: A-58 ASC-ECU 
connector, C-137 G and yaw rate sensor 
connector

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Repair the defective connector.

STEP 6. Check the harness wire between C-137 G 
and yaw rate sensor connector terminal No. 2, 3 
and A-58 ASC-ECU connector No. 18, 19.

• Check the communication lines for open circuit 

and short circuit.

Q: Is the check result normal?

YES : 

Go to Step 7.

NO : 

Repair the wiring harness, and then go to 
Step 13.

STEP 7. G and yaw rate sensor installation check
Check that the G and yaw rate sensor is installed 
correctly.

Q: Is the check result normal?

YES : 

Go to Step 8.

NO : 

Reinstall the G and yaw rate sensor 
correctly (Refer to 

P.35C-189

), and then go 

to Step 13.

STEP 8. Voltage measurement at C-137 G and 
yaw rate sensor connector
(1) Disconnect the C-137 G and yaw rate sensor 

connector.

(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between the terminal No.1 

and the body earth.

OK: Approximately system voltage

Q: Is the check result normal?

YES : 

Go to Step 11.

NO : 

Go to Step 9.

STEP 9. Voltage measurement at A-58 ASC-ECU 
connector
(1) Disconnect the ASC-ECU connector, connect the 

ASC check harness (Special tool: MB991997) to 
the ASC-ECU-side connector and harness-side 
connector, and then measure at the special tool 
connector side.

(2) Disconnect the C-137 G and yaw rate sensor 

connector.

(3) Turn the ignition switch to the "ON" position.

AC606870BQ

ASC-ECU

MB991997

Check harness

A-58 ASC-ECU
harness connector

(4) Measure the voltage between the terminal No.22 

and the body earth.

OK: Approximately system voltage

Q: Is the check result normal?

YES : 

Go to Step 12.

NO : 

Go to Step 10.

STEP 10. Wiring harness check between A-58 
ASC-ECU connector terminal No.22 and C-137 G 
and yaw rate sensor connector terminal No.1.

• Check the power supply circuit for short circuit.

Q: Is the check result normal?

YES : 

Go to Step 12.

NO : 

Repair the wiring harness between A-58 
ASC-ECU connector terminal No.22 and C-
137 G and yaw rate sensor connector 
terminal No.1.

STEP 11. Wiring harness check between A-58 
ASC-ECU connector terminal No.29 and C-137 G 
and yaw rate sensor connector terminal No.4.

• Check the earth circuit for open circuit.

Q: Is the check result normal?

YES : 

Replace the G and yaw rate sensor (Refer 

to 

P.35C-189

) and then go to Step 12.

NO : 

Repair the wiring harness between A-58 
ASC-ECU connector terminal No.29 and C-
137 G and yaw rate sensor connector 
terminal No.4.

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-119

STEP 12. Check whether the diagnosis code is 
reset.
(1) Erase the diagnosis code.
(2) Drive the vehicle at 20 km/h or higher.

Q: Are the diagnosis codes No.C2114 or C2115 set?

YES : 

Replace the hydraulic unit (integrated with 

ASC-ECU) (Refer to 

P.35C-185

), and then 

go to Step 13.

NO : 

Intermittent malfunction (Refer to GROUP 
00 

− How to Use Troubleshooting/How to 

Cope with Intermittent Malfunctions ).

STEP 13. Check whether the diagnosis code is 
reset.
(1) Erase the diagnosis code.
(2) Drive the vehicle at 20 km/h or higher.

Q: Are the diagnosis codes No.C2114 or C2115 set?

YES : 

Return to Step 1.

NO : 

This diagnosis is complete.

Code No. C123A: Abnormality in sensor calibration

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 steering wheel sensor is replaced, 

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

P.35C-

183

).

• 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 stores the calibrated value of the G and 
yaw rate sensor, steering wheel sensor, and brake 
fluid pressure sensor.

DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set when the calibrated value 
for each sensor stored in ASC-ECU is not within the 
predetermined range.

• Abnormality in neutral position of the G and yaw 

rate sensor

• Abnormality in neutral position of the steering 

wheel sensor

• Abnormality in neutral position of the brake fluid 

pressure sensor

PROBABLE CAUSES

• Improper installation of G and yaw rate sensor or 

steering wheel sensor

• ASC-ECU malfunction

• External noise interference

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 3.

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

Q: Is diagnosis code No.C123A set?

YES : 

Go to Step 3.

NO : 

This diagnosis is complete.

STEP 3. Check other diagnosis code is set.
Check if the diagnosis code related to the G and yaw 
rate sensor and the steering wheel sensor is set.

Q: Is any diagnosis code set?

YES : 

Perform the diagnosis for the relevant 

diagnosis code (Refer to 

P.35C-16

.)

NO : 

Go to Step 4.

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-120

STEP 4. G and yaw rate sensor calibration
Perform the calibration of G and yaw rate sensor 
(Refer to 

P.35C-182

.)

Q: Has the calibration succeeded?

YES : 

Go to Step 5.

NO : 

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

P.35C-185

), and then 

go to Step 8.

STEP 5. Steering wheel sensor calibration
Perform the calibration of steering wheel sensor 
(Refer to 

P.35C-183

).

Q: Has the calibration succeeded?

YES : 

Go to Step 6.

NO : 

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

P.35C-185

), and then 

go to Step 8.

STEP 6. Brake fluid pressure sensor calibration
Perform the calibration of brake fluid pressure sensor 
(Refer to 

P.35C-184

).

Q: Has the calibration succeeded?

YES : 

Go to Step 7.

NO : 

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

P.35C-185

), and then 

go to Step 8.

STEP 7. Check whether the diagnosis code is 
reset.
Erase the diagnosis code.

Q: Is diagnosis code No.C123A set?

NO : 

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

P.35C-185

), and then 

go to Step 8.

NO : 

Intermittent malfunction (Refer to GROUP 
00 

− How to Use Troubleshooting/How to 

Cope with Intermittent Malfunctions ).

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

Q: Is diagnosis code No.C123A set?

YES : 

Return to Step 1.

NO : 

This diagnosis is complete.

Code No. C1219 Abnormality in steering wheel sensor signal

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 steering wheel sensor is replaced, 

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

P.35C-

183

).

• 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
Steering wheel sensor outputs the signal to ASC-
ECU via the CAN bus lines.

DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set if any malfunction below is 
found:

• The tolerance of neutral position of steering 

wheel sensor exceeds the specified range.

• Abnormality in steering wheel sensor output 

value

• When abnormality is detected by comparing the 

value output from the steering wheel sensor with 
the one from the wheel speed sensor and the G 
and yaw rate sensor.

PROBABLE CAUSES

• Improper installation of steering wheel sensor

• Wheel alignment not performed

• Steering wheel sensor malfunction

• Different steering wheel

• G and yaw rate sensor malfunction

• Malfunction of wheel speed sensor

• ASC-ECU malfunction

• External noise interference