Mitsubishi Evolution X. Manual — part 803

DIAGNOSIS

TSB Revision

ACTIVE SKID CONTROL SYSTEM (ASC)

35C-219

TROUBLE SYMPTOM CHART

M1355006900190

CAUTION

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

high-speed turn, and bumpy road surface. When asking the customers, confirm if they have
encountered ABS operation in corresponding conditions.

• Even when the ASC operation display does not appear, the ASC operation noise (pump, motor,

and others) may be generated. This occurs because the pump, motor, and others operate to accu-
mulate the braking force before the application of braking force to wheels, and it is not a malfunc-
tion.

• During ABS operation, as the brake pedal is gradually drawn inward, the noise is generated. This

occurs because the brake line pressure varies intermittently to prevent the wheel lock, and it is
not a malfunction.

CAUTION

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

Trouble symptoms

Inspection
procedure
number

Reference
page

The scan tool cannot communicate
with the ABS/ASC system.

The scan tool cannot communicate
with all systems.

−

Refer to
GROUP 54C
−

Troubleshooti
ng

P.54C-14

.

The scan tool cannot communicate
only with ASC-ECU.

1

P.35C-220

With the parking brake released, the brake warning light remains illuminated
(ABS warning light is turned off).

2

P.35C-225

The ABS warning light does not illuminate when ignition switch is turned to
the ON position (engine stopped).

3

P.35C-228

The brake warning light does not illuminate when ignition switch is turned to
the ON position (engine stopped).

4

P.35C-230

The ABS warning light remains illuminated even after the engine is started.

5

P.35C-232

The ASC warning display remains illuminated even after the engine is
started.

6

P.35C-234

The ASC OFF display remains illuminated after the engine is started.

7

P.35C-237

After the ASC OFF switch is pressed to turn "OFF," the skid control/TCL
cannot be cancelled.

8

P.35C-239

Abnormality in brake operation

9

P.35C-241

Skid control/TCL does not operate.

10

P.35C-243

ASC-ECU power supply circuit system

11

P.35C-251

ABS/skid control/TCL operates too frequently.

12

P.35C-251

DIAGNOSIS

TSB Revision

ACTIVE SKID CONTROL SYSTEM (ASC)

35C-220

SYMPTOM PROCEDURES

Inspection Procedure 1: The scan tool cannot communicate with the ABS/ASC system.

CAUTION

• If there is any problem in the CAN bus lines, an incor-

rect diagnostic trouble code may be set. Prior to this
diagnosis, diagnose the CAN bus lines.

• Whenever the ECU is replaced, ensure that the CAN

bus lines are normal.

• If the power is supplied with the ground circuit of CAN

communication devices open circuited, a potential
abnormality may occur to the connected CAN bus line.

• When the hydraulic unit (integrated with ASC-ECU) is

replaced, always perform the calibration of steering
wheel sensor, G and yaw rate sensor, brake fluid pres-
sure sensor, cut valve, and inlet valve.(Refer to

P.35C-266

,

P.35C-267

,

P.35C-268

, and

P.35C-269

.)

.

TECHNICAL DESCRIPTION (COMMENT)

When the scan tool MB991958 cannot communicate with the
ABS/ASC system, there may be a malfunction to the CAN bus
lines, ASC-ECU power supply circuit system, ground, or
ASC-ECU.

.

PROBABLE CAUSES

• Damaged wiring harness and connectors

• ASC-ECU malfunction

• Wrong M.U.T.-III wiring harness

• Abnormality in battery or generator

• Abnormality in power supply voltage to ASC-ECU

• ECU malfunction of other system

DIAGNOSIS

Required Special Tools:

• MB991958: Scan Tool (M.U.T.-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: M.U.T.-III USB Cable

• MB991910: M.U.T.-III Main Harness A

Using scan tool MB991958, diagnose the CAN bus lines.
Using the scan tool, diagnose the CAN bus lines.
Q: Is the check result normal?

YES : Check and repair the power supply circuit system. (

Refer to

P.35C-243

.)

NO : Repair the CAN bus lines. (Refer to GROUP 54C

−

Troubleshooting

P.54C-14

.)

DIAGNOSIS

TSB Revision

ACTIVE SKID CONTROL SYSTEM (ASC)

35C-221

Inspection Procedure 2: With the parking brake released, the brake warning light remains illuminated
(ABS warning light is turned off).

CAUTION

• If there is any problem in the CAN bus lines, an incor-

rect diagnostic trouble code may be set. Prior to this
diagnosis, diagnose the CAN bus lines.

• Whenever the ECU is replaced, ensure that the commu-

nication circuit is normal.

.

CIRCUIT OPERATION

• When the parking brake switch is turned ON, the combina-

tion meter terminal No. 4 is grounded, and then the brake
warning light is illuminated.

• When the brake fluid level drop is detected, the brake fluid

level switch is turned from ON to OFF. ETACS-ECU moni-
tors the brake fluid level switch, and gives an instruction via
the CAN bus line to the combination meter to illuminate the
brake warning light.

.

PROBABLE CAUSES

• The brake pad thickness is at the limit value or less.

• The brake fluid amount is at the "LOWER" level or lower.

• Poor adjustment of the parking brake lever

• Damaged wiring harness and connectors

• Parking brake switch malfunction

• Brake fluid level switch malfunction

• Combination meter malfunction

• ETACS-ECU malfunction

AC708972AP

Connector: C-312

ETACS-ECU

AC708949

Connector: A-09

AF

AC708950

Connector: C-04

AR

AC708951AN

C-23

C-122

Connectors: C-23, C-122

DIAGNOSIS

TSB Revision

ACTIVE SKID CONTROL SYSTEM (ASC)

35C-222

DIAGNOSIS

Required Special Tools:

• MB991958 Scan Tool (M.U.T.-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827 M.U.T.-III USB Cable

• MB991910 M.U.T.-III Main Harness A

STEP 1. Using scan tool MB991958, diagnose the CAN bus
lines.
Using scan tool MB991958, 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

−

Troubleshooting

P.54C-14

.)

STEP 2. Scan tool diagnostic trouble code for other
systems
Using scan tool MB991958, check if the diagnostic trouble
code is set in the combination meter and ETACS-ECU.
Q: Is any DTC set?

YES : Carry out the diagnosis for the DTC.
NO : Go to Step 3.

STEP 3. Brake fluid level check
Check that the brake fluid is filled up to the "MIN" level or
higher.
Q: Is the check result normal?

YES : Go to Step 5.
NO : Go to Step 4.

STEP 4. Brake pad check
Refer to GROUP 35A

− On-vehicle Service, Brake Pad Check

P.35A-17

.

Q: Is the check result normal?

YES : Fill the brake fluid up to the "MAX" level. Then go to

Step 18.

NO : Replace the brake pad. (Refer to GROUP 35A

−

On-vehicle Service, Brake Pad Replacement

P.35A-18

.) Then, go to Step 18.

STEP 5. Brake fluid level switch check
Refer to GROUP 35A

− On-vehicle Service, Brake Fluid Level

Switch Check

P.35A-17

.

Q: Is the check result normal?

YES : Go to Step 6.
NO : Replace the reservoir tank assembly. (Refer to

GROUP 35A

− Master Cylinder Assembly and Brake

Booster Assembly

P.35A-27

.) Then, go to Step 18.