Mitsubishi Evolution X. Manual — part 771

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-91

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 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.27-33

.)

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.27-36

.)

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.27-36

.)

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-272

.) Then go to Step 6.

NO : Intermittent malfunction. (Refer to GROUP 00

− How

to Cope with Intermittent Malfunction

P.00-15

.)

AC608248AB

Magnetic
encoder

Rear Wheel
bearing

Rear wheel
hub
assembly

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-92

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.

DTC C1046: FL wheel speed sensor control phase time exceeded

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

AC708949

Connector: A-11

A-11 (B)

AB

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-93

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

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 C1046 set?

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

DIAGNOSIS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-94

STEP 3. Scan tool diagnostic trouble code
Check whether DTC No. C100A, C1011, C1014, and C1041
are simultaneously set.
Q: Are DTC C100A, C1011, C1014, and C1041 also set?

YES : Carry out the diagnosis for the diagnostic trouble

codes that are set, and then go to Step 5.

NO : Go to Step 4.

STEP 4. Scan tool service data
Check the following service data. (Refer to

P.35C-255

.)

• Item No.01: FL wheel speed sensor

Q: Is the check result normal?

YES : Go to Step 16.
NO : Go to Step 5.

STEP 5. 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. 45 and the body
ground as well as between the ground terminal No. 46 and
the body ground.

OK: 1 volt or less

Q: Is the check result normal?

YES : Go to Step 6.
NO (Not normal at the terminal No. 45 or 46) : Go to Step

7.

AC400817CB

ASC-ECU

MB991997

Check harness

A-05 ASC-ECU
harness connector