Mitsubishi Evolution X. Manual — part 755

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-27

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 <FL>. (Refer to

P.35C-274

.) Then go to Step 13.

STEP 11. Connector check: A-05 ASC-ECU connector, A-11
wheel speed sensor <FL> 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 C100A 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 C100A set?

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

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-28

DTC C1015: Abnormality in FR 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.

.

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

AC708948

A-05 (B)

AC

Connectors: A-03, A-05

A-03 (B)

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-29

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 No. C1015 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.02: FR wheel speed sensor

Q: Is the check result normal?

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

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-30

STEP 4. Voltage measurement at A-05 ASC-ECU connector
(1) Disconnect the ASC-ECU connector, connect the ASC

check harness (Special tool: MB991997) to the wiring
harness-side connector, and then measure at the special
tool connector side.
NOTE: Do not connect the special tool to ASC-ECU.

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

power supply terminal (signal terminal) No. 34 and the body
ground as well as between the ground terminal No. 33 and
the body ground.

OK: 1 volt or less

Q: Is the check result normal?

YES : Go to Step 5.
NO (Not normal at terminal 34 or 33) : Go to Step 6.

STEP 5. Resistance measurement at A-05 ASC-ECU
connector
(1) Disconnect the ASC-ECU connector, connect the ASC

check harness (Special tool: MB991997) to the wiring
harness-side connector, and then measure at the special
tool connector side.
NOTE: Do not connect the special tool to ASC-ECU.

(2) Measure the resistance between the wheel speed sensor

circuit power supply terminal (signal terminal) No. 34 and
the body ground as well as between the ground terminal
No. 33 and the body ground.

OK: No continuity

Q: Is the check result normal?

YES : Go to Step 8.
NO (Not normal at terminal 34 or 33) : Go to Step 6.

AC400817CE

ASC-ECU

MB991997

Check harness

A-05 ASC-ECU
harness connector

AC400817CF

ASC-ECU

MB991997

Check harness

A-05 ASC-ECU
harness connector