Mitsubishi Colt Ralliart. Manual - part 638

TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-97

COMMENTS ON TROUBLE SYMPTOM

• The brake warning lamp drive signal at the EBD 

system error and the low brake fluid level is sent 
from the ASC-ECU to the combination meter 
through the CAN communication lines.

• If the combination meter detects a ASC time-out 

due to a failure in the power supply to the 
ASC-ECU or abnormal CAN communication, the 
combination meter illuminates the lamp.

• The ASC-ECU sends the lamp drive signal to the 

combination meter during a bulb check (for three 
seconds after the ignition switch is turned on) 
through the CAN communication lines, and then 
the combination meter activates the lamp.

• If the combination meter detects a ASC time-out 

due to a failure in abnormal CAN communication, 
the combination meter illuminates the lamp.

• This symptom appears when the brake fluid level 

switch or the parking brake switch is shorted to 
earth. When the brake fluid level witch is shorted 
to earth, the diagnosis code No. C1345 is set.

PROBABLE CAUSES

• Damaged wiring harness and connectors

• Parking brake switch malfunction

• Brake fluid level switch malfunction

• Combination meter assembly malfunction

• ASC-ECU malfunction

DIAGNOSTIC PROCEDURE

STEP 1. Check the brake fluid level.
Check that the brake fluid is filled to the specified.

Q: Is the check result normal?

YES : 

Check the brake pad remaining thickness, 

fill the brake fluid to the specified, and then 
go to Step 12.

NO : 

Go to Step 2.

STEP 2. M.U.T.-III data list
Using the data list, check that the parking brake input 
signal and the brake fluid level switch signal are nor-
mal.(Refer to 

P.35C-109

.)

• Item No. 28: Side brake switch

• Item No. 32: Brake fluid level switch

Q: Is the check result normal?

YES : 

Go to Step 10.

NO : 

Go to Step 3.

STEP 3. Check the brake fluid level switch as a 
single unit.
Refer to GROUP 35A 

− On-vehicle Service 

P.35A-11

.

Q: Is the check result normal?

YES : 

Go to Step 4.

NO : 

Replace the reservoir assembly. (Refer to 
GROUP 35A 

− Master cylinder assembly 

and brake booster 

P.35A-23

.)

STEP 4. Check A-03 brake fluid level switch 
connector and A-05 ASC-ECU connector.

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Repair the A-03 brake fluid level switch 
connector and the A-05 ASC-ECU 
connector.

AC601084

Connector: A-03

AD

A-03(Grey)

Harness 
side

AC601083

Connector: A-05

AB

A-05(Black)

Harness side

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TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-98

STEP 5. Measure the resistance at A-03 brake 
fluid level switch connector and A-05 ASC-ECU 
connector.

(1) Disconnect A-03 brake fluid level switch 

connector and A-05 ASC-ECU connector.

(2) Make the brake fluid below the specified level, 

and turn ON the brake fluid level switch.

(3) Measure the resistance between A-03 brake fluid 

level switch connector terminal No. 2 and A-05 
ASC-ECU connector terminal No. 32.

OK: Continuity exists (2 

Ω or less)

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Repair the harness wire between A-03 
brake fluid level switch connector terminal 
No. 2 and A-05 ASC-ECU connector 
terminal No. 32.

STEP 6. Measure the resistance at A-03 brake 
fluid level switch connector.

(1) Disconnect A-03 brake fluid level switch 

connector.

(2) Measure the resistance between A-03 brake fluid 

level switch connector terminal No. 2 and the 
body earth.

OK: Continuity exists (2 

Ω or less)

Q: Is the check result normal?

YES : 

Go to Step 7.

NO : 

Repair the harness wire between A-03 
brake fluid level switch connector terminal 
No. 2 and body earth.

STEP 7. Check the parking brake switch as single 
unit.
Refer to GROUP 36 

− On-vehicle Service 

P.36-5

.

Q: Is the check result normal?

YES : 

Go to Step 8.

NO : 

Replace the parking brake switch. (Refer to 
GROUP 36 

− Parking brake lever 

P.36-7

.)

AC601110

Connector: A-03, A-05

A-05
(Black)

A-03(Grey)

AB

A-03: Harness side

A-05: Harness side

AC601084

Connector: A-03

AE

A-03(Grey)

Harness side

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TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-99

STEP 8. Check A-05 ASC-ECU connector and 
C-42 parking brake switch connector.

Q: Is the check result normal?

YES : 

Go to Step 9.

NO : 

Repair.

STEP 9. Measure the resistance at A-05 ASC-ECU 
connector.

(1) Disconnect the A-05 ASC-ECU connector.
(2) Pull the parking brake lever and turn the parking 

brake switch to ON.

(3) Measure the resistance between A-05 ASC-ECU 

connector terminal No. 27 and the body earth.

OK: Continuity exists (2 

Ω or less)

Q: Is the check result normal?

YES : 

Go to Step 12.

NO : 

Repair the harness wire between A-05 
ASC-ECU connector terminal No. 27 and 
C-42 parking brake switch connector 
terminal No. 1.

AC601083

Connector: A-05

AB

A-05(Black)

Harness side

AC601093

Connector: C-44

AD

C-44(Black)

Harness side

AC601083

Connector: A-05

AB

A-05(Black)

Harness side

AC601085

AC601085AJ

MB991984

ASC-ECU

Check connector

ASC-ECU harness connector

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TROUBLESHOOTING

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-100

STEP 10. Retest the system.

Q: Does the brake warning lamp go off when the 

ignition switch is ON?
YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Cope with Intermittent 

Malfunction 

P.00-13

.)

NO : 

Replace the combination meter assembly, 
and then go to Step 11.

STEP 11. Retest the system.

Q: Does the brake warning lamp go off when the 

ignition switch is ON?
YES : 

This diagnosis is complete.

NO : 

Replace the ASC-ECU.

STEP 12. Retest the system.

Q: Does the brake warning lamp go off when the 

ignition switch is ON?
YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Cope with Intermittent 

Malfunction 

P.00-13

.)

NO : 

Replace the ASC-ECU.

Inspection Procedure 9: The stability control system operates too frequently. (the diagnosis code is 
not set.)

COMMENTS ON TROUBLE SYMPTOM

• This symptom does not appear due to a failure in 

wiring harness (open or short circuit, or excessive 
resistance). Therefore, if the sensors are installed 
properly and the check result does not indicate 
any problems, replace the ASC-ECU.

• This symptom does not appear at steering wheel 

sensor calibration. (The diagnosis code is set.)

NOTE: If the steering neutral position fluctuates 

slightly, the ASC system may activate early.

PROBABLE CAUSES

• Wheel speed sensor malfunction

• G and yaw rate sensor malfunction

• Steering wheel sensor malfunction

• Wheel bearing malfunction

• ASC-ECU malfunction

• Malfunction of magnetic encoder for wheel speed 

detection

DIAGNOSTIC PROCEDURE

STEP 1. 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 2.

NO : 

Reinstall the G and yaw rate sensor 
correctly.

STEP 2. M.U.T.-III data list
Using the data list, check the G and yaw rate sensor 
output value.(Refer to 

P.35C-109

.)

• Item No. 14: Lateral G-sensor

• Item No.17: Yaw rate sensor

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Replace the G and yaw rate sensor.

STEP 3. Steering wheel sensor installation state 
check
Check that the steering wheel sensor is installed cor-
rectly.

Q: Is the check result normal?

YES : 

Go to Step 4.

NO : 

Install the steering wheel sensor correctly.

STEP 4. M.U.T.-III data list
Using the data list, check the steering sensor output 
value.(Refer to 

P.35C-109

.)

• Item No. 16: Steering angle sensor

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Replace the steering wheel sensor.

STEP 5. Check how wheel speed sensor is 
installed.
Check that the wheel speed sensor is installed cor-
rectly.

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Reinstall the wheel speed sensor correctly.

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