Mitsubishi Evolution X. Manual — part 756

DIAGNOSIS

TSB Revision

ACTIVE SKID CONTROL SYSTEM (ASC)

35C-31

STEP 6. Connector check: A-05 ASC-ECU connector, A-03
wheel speed sensor <FR> connector
Q: Is the check result normal?

YES : Go to Step 7.
NO : Repair the defective connector. Then go to Step 13.

STEP 7. Wiring harness check between A-05 ASC-ECU
connector terminal No. 34 and A-03 wheel speed sensor
<FR> connector terminal No. 1, and between A-05
ASC-ECU connector terminal No. 33 and A-03 wheel speed
sensor <FR> connector terminal No. 2

• Short circuit check of wheel speed sensor <FR> circuit

Q: Is the check result normal?

YES : Replace the wheel speed sensor <FR>. (Refer to

P.35C-274

.) Then go to Step 13.

NO : Repair the wiring harness. Then go to Step 13.

STEP 8. Voltage measurement at A-05 ASC-ECU connector
(1) Disconnect the ASC-ECU connector, connect the ASC

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

(2) Turn the ignition switch to the ON position.
(3) Measure the voltage between the wheel speed sensor

circuit power supply terminal (signal terminal) No. 34 and
the body ground.

OK: System voltage

Q: Is the check result normal?

YES : Go to Step 9.
NO : Go to Step 11.

STEP 9. Wiring harness check between A-05 ASC-ECU
connector terminal No. 34 and A-03 wheel speed sensor
<FR> connector terminal No. 1, and between A-05
ASC-ECU connector terminal No. 33 and A-03 wheel speed
sensor <FR> connector terminal No. 2

• Open circuit check of wheel speed sensor <FR> circuit

Q: Is the check result normal?

YES : Go to Step 10.
NO : Repair the wiring harness. Then go to Step 13.

AC400817CG

ASC-ECU

MB991997

Check harness

A-05 ASC-ECU
harness connector

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-32

STEP 10. Check of wheel speed sensor as a single unit
Refer to

P.35C-277

.

Q: Is the check result normal?

YES : Go to Step 11.
NO : Replace the wheel speed sensor <FR>. (Refer to

P.35C-274

.) Then go to Step 13.

STEP 11. Connector check: A-05 ASC-ECU connector, A-03
wheel speed sensor <FR> connector
Q: Is the check result normal?

YES : Go to Step 12.
NO : Repair the defective connector. Then go to Step 13.

STEP 12. Check whether the DTC is reset.
Drive the vehicle at 12mph (20 km/h) or more.
NOTE: The ABS warning light does not turn OFF in some
cases unless the vehicle runs at 12mph (20 km/h) or higher.
Q: Is DTC C1015 set?

YES : Replace the hydraulic unit (incorporates in

ASC-ECU).(Refer to

P.35C-272

.) Then go to Step 13.

NO : Intermittent malfunction. (Refer to GROUP 00

− How

to Cope with Intermittent Malfunction

P.00-15

.)

STEP 13. Check whether the DTC is reset.
Drive the vehicle at 12mph (20 km/h) or more.
NOTE: The ABS warning light does not turn OFF in some
cases unless the vehicle runs at 12mph (20 km/h) or higher.
Q: Is DTC C1015 set?

YES : Return to Step 1.
NO : This diagnosis is complete.

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-33

DTC C1020: Abnormality in RL wheel speed sensor circuit

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.

• 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

.)

.

CIRCUIT OPERATION

• Each wheel speed detecting section is a kind of a pulse

generator. It consists of the encoder (plate on which the
north and south pole of magnet are arranged alternately) for
detecting the wheel speed, which rotates at the same speed
of the wheels, and the wheel speed sensor. This detecting
section outputs the frequency pulse signals in proportion to
the wheel speed.

• The pulse signals generated by the wheel speed detecting

section are sent to ASC-ECU. ASC-ECU uses the fre-
quency of the pulse signals to determine the wheel speed.

.

AC708948

Connector: A-05

A-05 (B)

AB

AC708950

Connector: C-45

AD

AC708955

Connector: D-18

D-18 (B)

AE

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-34

DTC SET CONDITIONS

ASC-ECU monitors the electric current in each wheel speed
sensor circuit. If an open or short circuit in the wheel speed
sensor circuit is detected, ASC-ECU sets a corresponding
diagnostic trouble code.

.

PROBABLE CAUSES

Current trouble

• Damaged wiring harness and connectors

• Noise interference

• Malfunction of wheel speed sensor

• ASC-ECU malfunction

Past trouble

• Carry out the diagnosis with a particular emphasis on the

wiring harness and connector failures between ASC-ECU
and the wheel speed sensor. For diagnosis procedures,
refer to How to Treat Past Trouble (GROUP 00

− How to

Use Troubleshooting/Inspection Service Points

P.00-16

).

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

• MB991997: ASC check harness

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 3.
NO : Repair the CAN bus lines. (Refer to GROUP 54C

−

Troubleshooting

P.54C-14

.) After repairing the CAN

bus line, go to Step 2.

STEP 2. DTC recheck after repairing the CAN bus line
Q: Is DTC C1020 set?

YES : Go to Step 3.
NO : This diagnosis is complete.

STEP 3. Scan tool service data
Check the following service data. (Refer to

P.35C-255

.)

• Item No.03: RL wheel speed sensor

Q: Is the check result normal?

YES : Go to Step 12.
NO : Go to Step 4.