Active Stability Control System (ASC)
Code No. C102A: Mutual monitoring of RL wheel speed sensor
CAUTION:
- If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnosis, diagnose the CAN bus lines Initial Inspection and Diagnostic Overview ).
- Whenever ECU is replaced, ensure that the CAN bus lines are normal.
- When the hydraulic unit (integrated with ASC-ECU) is replaced, always carry out the calibration of the steering wheel sensor, the G and yaw rate sensor and brake fluid pressure sensor (Refer to G and Yaw Rate Sensor Calibration , Testing and Inspection and Master Cylinder Brake Fluid Pressure Sensor Calibration ).
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 frequency 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 fault below is found in these sensor signals, ASC-ECU will set the relevant DTC.
- Missing wheel speed sensor signal
- Wheel speed sensor signal continuously indicates low value.
PROBABLE CAUSES
Current trouble
- Excessive gap between the wheel speed sensor and the wheel speed detection encoder
- Adhesion of foreign materials on the wheel speed sensor
- Wheel bearing malfunction
- Deformation of the wheel speed detection encoder
- Adhesion of foreign materials on the wheel speed detection encoder
- Malfunction of wheel speed sensor
- Improper installation of the wheel speed sensor
- ASC-ECU malfunction
- The number of poles on the Magnetic encoder for wheel speed detection (N-pole and S-pole) is changed
Past trouble
- When DTC C1020 is also set, carry out diagnosis with particular emphasis on wiring harness and connector failures between ASC-ECU and the wheel speed sensor. For diagnosis procedures, refer to How to treat past trouble How to Treat Past Trouble ).
- When DTC C1020 is not set, the following conditions may be present:
- Some wheels slip
- Unstable vehicle attitude
- External noise interference
- Vehicle ran with the parking brake applied.
- Rotate only two wheels with drum tester
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
STEP 1. Using scan tool MB991958, diagnose the CAN bus lines.
Use scan tool to diagnose the CAN bus lines.
Q. Is the check result normal?
YES Go to Step 3.
NO Repair the CAN bus lines CAN Bus Diagnostics Chart).
On completion, go to Step 2.
STEP 2. DTC recheck after resetting CAN bus lines
Q. Is DTC C102A set?
YES Go to Step 3.
NO The procedure is complete.
STEP 3. Using scan tool MB991958, check the DTC
Check that the DTC C1020 is also set.
Q. Is DTC C1020 also set?
YES Perform the diagnosis for the DTC C1020 (Refer to Active Stability Control System (ASC)).
NO Go to Step 4.
STEP 4. Check for wheel speed sensor installation
Check how the wheel speed sensor [RL] is installed (Disconnection of wheel speed sensor, loose mounting bolt, etc.).
Q. Is the check result normal?
YES Go to Step 5.
NO Reinstall the wheel speed sensor [RL] correctly (Refer to Service and Repair).
Then go to Step 5.
STEP 5. Check for wheel speed sensor output current
Refer to Wheel Speed Sensor Output Current Measurement.
Q. Is the check result normal?
YES Go to Step 6.
NO Replace the wheel speed sensor [RL] (Refer to Service and Repair). Then go to Step 9.
STEP 6. Wheel bearing looseness check
NOTE:
- Wheel bearing looseness may increase the gap between the wheel speed sensor and the wheel speed detection magnet encoder.
- Check the wheel bearing[ RL] for looseness. Rear Axle .)
Q. Is the check result normal?
YES Go to Step 7.
NO Replace the rear wheel hub assembly Rear Axle). Then go to Step 10.
STEP 7. Check of wheel speed detection encoder
Check the encoder for adhesion of foreign materials or deformation.
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. Then go to Step 10
.
NO (Deformation) : Replace the rear wheel hub assembly. Rear Axle.) Then go to Step 10.
STEP 8. 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 C102A set?
YES Replace the wheel speed sensor (Refer to Service and Repair).
Then go to Step 9.
NO Intermittent malfunction How to Cope With Intermittent Malfunctions).
STEP 9. Check whether the DTC is reset.
(1)Erase the DTC.
(2)Drive the vehicle at 12 mph (20 km/h) or more.
NOTE:
The ABS warning light does not turn OFF in some cases unless the vehicle runs at 12 mph
(20 km/h) or higher.
Q. Is DTC C102A set?
YES Replace the hydraulic unit (ASC-ECU) (Refer to Service and Repair). Then go to Step 10.
NO The procedure is complete.
STEP 10. Check whether the DTC is reset.
(1)Erase the DTC.
(2)Drive the vehicle at 12 mph (20 km/h) or more.
NOTE:
The ABS warning light does not turn OFF in some cases unless the vehicle runs at 12 mph
(20 km/h) or higher.
Q. Is DTC C102A set?
YES Return to Step 1.
NO The procedure is complete.