Mitsubishi Lancer Evolution X. Manual — part 142

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-33

STEP 6. Resistance measurement at A-05 ASC-ECU
connector
(1) Disconnect the ASC-ECU connector, connect the special

tool ASC check harness (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 7.
NO (Not normal at the terminal No. 34 or 33) : Go to Step

8.

STEP 7. Voltage measurement at A-05 ASC-ECU connector
(1) Disconnect the ASC-ECU connector, connect special tool

ASC check harness (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 and between the wheel speed sensor
circuit ground terminal No. 33 and the body ground.

OK:

Terminal No.34 and the body ground: Battery

positive voltage

Terminal No.33 and the body ground: 1 V or less

Q: Is the check result normal?

YES : Go to Step 8.
NO : Go to Step 10.

AC400817CF

ASC-ECU

MB991997

Check harness

A-05 ASC-ECU
harness connector

AC400817CG

ASC-ECU

MB991997

Check harness

A-05 ASC-ECU
harness connector

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-34

STEP 8. Check of wheel speed sensor as a single unit
Refer to

P.35C-303

.

Q: Is the check result normal?

YES : Go to Step 9.
NO : Replace the wheel speed sensor <FR>. (Refer to

P.35C-300

.) Then 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

• Check for short or open circuit in 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 11.

STEP 10. Check whether the DTC is reset.
(1) Erase the DTC.
(2) 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-298

.) Then go to Step 11.

NO : Intermittent malfunction. (Refer to GROUP 00 − How

to Cope with Intermittent Malfunction

P.00-15

.)

STEP 11. Check whether the DTC is reset.
(1) Erase the DTC.
(2) 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 STABILITY CONTROL SYSTEM (ASC)

35C-35

DTC C1020: Abnormality in RL wheel speed sensor circuit

ASC-ECU

(LH)

(LH)

(RH)

(RH)

FRONT WHEEL SPEED SENSOR

REAR WHEEL SPEED SENSOR

Wheel Speed Sensor Circuit

AC804587

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 STABILITY CONTROL SYSTEM (ASC)

35C-36

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-287

,

P.35C-289

,

P.35C-294

, and

P.35C-295

.)

.

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

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