Mitsubishi Lancer Evolution X. Manual — part 152

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-73

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 signals from each wheel speed sensor
while the vehicle is being driven. If any abnormality below is
detected in the sensor signals, ASC-ECU sets the relevant
diagnostic trouble code.

• Missing wheel speed sensor signal
• Wheel speed sensor signal continuously indicates lower

value than the values of other wheel speed sensors.

.

PROBABLE CAUSES

Current trouble

• Excessive gap between the wheel speed sensor and the

magnetic encoder for wheel speed detection

• Wheel bearing malfunction
• Deformation of 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

• Malfunction of wheel speed sensor
• Improper installation of the wheel speed sensor
• ASC-ECU malfunction
• Disturbance of magnetization pattern for magnetic encoder

for wheel speed detection

• The number of poles on the magnetic encoder for wheel

speed detection (the number of N-pole and S-pole) is
changed.

Past trouble

• When the DTC No. C100A is also set, perform the diagno-

sis 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 Troubleshoot-

ing/Inspection Service Points

P.00-16

).

• When DTC No. C100A is not set simultaneously, the follow-

ings can be suspected.

• Wheel(s) spinning
• Unstable vehicle attitude (spin)
• External noise interference
• Vehicle ran with the parking brake applied.
• Only two wheels are rotated on a drum tester.

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-74

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 C1014 set?

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

STEP 3. Scan tool diagnostic trouble code
Check if DTC No. C100A is also set.
Q: Is DTC C100A also set?

YES : Carry out the diagnosis for code No. C100A. ( Refer

to

P.35C-25

.)

NO : Go to Step 4.

STEP 4. Check of wheel speed sensor installation status
Check the installation status of wheel speed sensor <FL> (dis-
connection of wheel speed sensor, looseness of mounting bolt,
etc.).
Q: Is the check result normal?

YES : Go to Step 5.
NO : Reinstall the wheel speed sensor <FL> correctly.

(Refer to

P.35C-300

.) Then go to Step 9.

STEP 5. Check of wheel speed sensor as a single unit
Refer to

P.35C-303

.

Q: Is the check result normal?

YES : Go to Step 6.
NO : Replace the wheel speed sensor <FL>. (Refer to

P.35C-300

.) Then go to Step 9.

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-75

STEP 6. 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 <FL> for loose-
ness. (Refer to GROUP 26

−

On-vehicle Service

P.26-7

.)

Q: Is the check result normal?

YES : Go to Step 7.
NO : Replace the front hub assembly. (Refer to GROUP 26

− Front Axle Hub Assembly

P.26-9

.)

STEP 7. 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 8.
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 front hub assembly. (Refer

to GROUP 26 − Front Axle Hub Assembly

P.26-9

.)

STEP 8. 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 C1014 set?

YES : Replace the hydraulic unit (incorporates in

ASC-ECU).(Refer to

P.35C-298

.) Then go to Step 9.

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

to Cope with Intermittent Malfunction

P.00-15

.)

STEP 9. 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 C1014 set?

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

AC704652 AB

Oil seal

Magnetic
encoder

Wheel
bearing

Hub

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-76

DTC C101F: Mutual monitoring of FR wheel speed sensor

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 signals from each wheel speed sensor
while the vehicle is being driven. If any abnormality below is
detected in the sensor signals, ASC-ECU sets the relevant
diagnostic trouble code.

• Missing wheel speed sensor signal
• Wheel speed sensor signal continuously indicates lower

value than the values of other wheel speed sensors.

.

PROBABLE CAUSES

Current trouble

• Excessive gap between the wheel speed sensor and the

magnetic encoder for wheel speed detection

• Wheel bearing malfunction
• Deformation of 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

• Malfunction of wheel speed sensor
• Improper installation of the wheel speed sensor
• ABS-ECU malfunction
• Disturbance of magnetization pattern for magnetic encoder

for wheel speed detection