Mitsubishi Lancer Evolution X. Manual — part 157

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-93

DTC SET CONDITIONS

ASC-ECU monitors the signals from each wheel speed sensor
while the vehicle is being driven. If any periodical drop abnor-
mality is detected in the sensor signals, ASC-ECU sets the rel-
evant diagnostic trouble code.

.

PROBABLE CAUSES

• Wheel bearing malfunction
• Deformation of the magnetic encoder for wheel speed

detection

• Adhesion of foreign materials on the magnetic encoder for

wheel speed detection

• ABS-ECU malfunction
• Disturbance of magnetization pattern for magnetic encoder

for wheel speed detection

• Missing teeth of the magnetic encoder for wheel speed

detection

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-15

.) After repairing the CAN

bus line, go to Step 2.

STEP 2. DTC recheck after repairing the CAN bus line
Q: Is DTC C1044 set?

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

STEP 3. Wheel bearing looseness check
NOTE: Wheel bearing looseness may increase the gap
between the wheel speed sensor and the wheel speed detec-
tion magnet encoder. Check the wheel bearing <RR> for loose-
ness. (Refer to GROUP 27

−

On-vehicle Service

P.27-32

.)

Q: Is the check result normal?

YES : Go to Step 4.
NO : Replace the rear wheel hub assembly. (Refer to

GROUP 27 − Rear Axle Hub Assembly

P.27-35

.)

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-94

STEP 4. Check of wheel speed detection encoder
Check the encoder for adhesion of foreign materials or defor-
mation.
Q: Is the check result normal?

YES : Go to Step 5.
NO (Adhesion of foreign materials) : Clean the encoder

so as not to disturb the magnetization pattern on the
encoder while taking care of the magnet, magnetic
substance, and magnetic attraction.

NO (Deformation) : Replace the rear wheel hub assembly.

(Refer to GROUP 27 − Rear Axle Hub Assembly

P.27-35

.)

STEP 5. Check whether the DTC is reset.
(1) Erase the diagnostic trouble code.
(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 C1044 set?

YES : Replace the hydraulic unit (incorporates in

ASC-ECU).(Refer to

P.35C-298

.) Then go to Step 6.

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

to Cope with Intermittent Malfunction

P.00-15

.)

STEP 6. Check whether the DTC is reset.
(1) Erase the diagnostic trouble code.
(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 C1044 set?

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

AC608248AB

Magnetic
encoder

Rear Wheel
bearing

Rear wheel
hub
assembly

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-95

DTC C1046: FL wheel speed sensor control phase time exceeded

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

AC708949

Connector: A-11

A-11 (B)

AB

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-96

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

This diagnostic trouble code is set if any malfunction below is
detected.

• When the brake fluid pressure is decreased for a long time.
• When the brake fluid pressure is held for a long time.

NOTE: ASC controls the vehicle based on the wheel speed sig-
nal. When the brake fluid pressure is decreased or held for an
abnormally long time, the wheel speed sensor signal may have
a problem.

.

PROBABLE CAUSES

• Damaged wiring harness and connectors
• External noise interference
• Malfunction of wheel speed sensor
• ABS-ECU malfunction
• Excessive gap between the wheel speed sensor and the

magnetic encoder for wheel speed detection

• Adhesion of foreign materials on the wheel speed sensor
• Adhesion of foreign materials on the magnetic encoder for

wheel speed detection

• Wheel bearing malfunction
• Improper installation of the wheel speed sensor
• Deformation of the magnetic encoder for wheel speed

detection

• Disturbance of magnetization pattern for magnetic encoder

for wheel speed detection

• Missing teeth of the magnetic encoder for wheel speed

detection