Active Stability Control System (ASC)
DTC C101C: Abnormality in FR wheel speed sensor signal
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 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 pressure sensor, cut valve, and inlet valve (Refer to G and Yaw Rate Sensor Calibration , Testing and Inspection , Master Cylinder Brake Fluid Pressure Sensor Calibration , and Testing and Inspection ).
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 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 abnormality below is detected in the sensor signals, ASC-ECU sets the relevant diagnostic trouble code.
- Irregular change in the wheel speed sensor signal
- Wheel speed sensor signal continuously indicates higher 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
- Adhesion of foreign materials on the wheel speed sensor
- Adhesion of foreign materials on the magnetic encoder for wheel speed detection
- Wheel bearing malfunction
- Malfunction of wheel speed sensor
- Damaged wiring harness and connectors
- External noise interference
- Improper installation of the wheel speed sensor
- Deformation of the magnetic encoder for wheel speed detection
- 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. C1015 is also set, perform 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 How to Treat Past Trouble ).
- When diagnostic trouble code No.C1015 is not set, the following conditions may be present:
- Wheel(s) spinning
- Unstable vehicle attitude (spin)
- External noise interference
- Vehicle ran with the parking brake applied.
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 C101C set?
YES Go to Step 3.
NO The procedure is complete.
STEP 3. Using scan tool MB991958, check the DTC
Check that DTC C1015 is also set.
Q. Is DTC C1015 also set?
YES Perform the diagnosis for DTC C1015 (Refer to Active Stability Control System (ASC)).
NO Go to Step 4.
STEP 4. Connector check: A-05 ASC-ECU connector, A-03 front wheel speed sensor [RH] connector
Q. Is the check result normal?
YES Go to Step 5.
NO Repair the defective connector. Then go to Step 12.
STEP 5. Wiring harness check between A-05 ASC-ECU connector terminal No. 34 and A-03 front wheel speed sensor [RH] connector terminal No. 1, and between A-05 ASC-ECU connector terminal No. 33 and A-03 front wheel speed sensor [RH] connector terminal No. 2
Q. Is the check result normal?
YES Go to Step 6.
NO Repair the wiring harness. Then go to Step 12.
STEP 6. Check for wheel speed sensor [FR] installation
Check how the wheel speed sensor [FR] is installed (Disconnection of wheel speed sensor [FR], loose mounting bolt, etc.).
Q. Is the check result normal?
YES Go to Step 7.
NO Reinstall the wheel speed sensor [FR] correctly (Refer to Service and Repair).
Then go to Step 7.
STEP 7. Check for wheel speed sensor [FR] output current
Refer to Wheel Speed Sensor Output Current Measurement.
Q. Is the check result normal?
YES Go to Step 8.
NO Replace the wheel speed sensor [FR] (Refer to Service and Repair). Then go to Step 11.
STEP 8. Check for wheel bearing looseness
NOTE:
- Loose wheel bearing may increase the gap between the wheel speed sensor[ FR] and the wheel speed detection magnet encoder.
- Check the wheel bearing[ FR] for looseness Front Axle ).
Q. Is the check result normal?
YES Go to Step 9.
NO Replace the front hub assembly [FR] Front Axle Hub Assembly Removal and Installation [Flange Nut Type]). Then go to Step 12.
STEP 9. 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 10.
NO (Adhesion of foreign materials) : Remove the foreign materials and clean the encoder so as not to disturb the magnetization pattern on it while taking care of the magnet, magnetic substance, and magnetic attraction.
Then go to Step 12.
NO (Deformation) : Replace the front hub assembly [FR] Front Axle Hub Assembly Removal and Installation [Flange Nut Type]). Then go to Step 12.
STEP 10. Check whether the DTC is reset.
(1)Erase the DTC.
(2)Drive the vehicle at 12mph (20 km/h) or higher.
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 C101C set?
YES Replace the wheel speed sensor [FR] (Refer to Service and Repair).
Then go to Step 11.
NO Intermittent malfunction How to Cope With Intermittent Malfunctions).
STEP 11. Check whether the DTC is reset.
(1)Erase the DTC.
(2)Drive the vehicle at 12 mph (20 km/h) or higher.
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 C101C set?
YES Replace the hydraulic unit (integrated with ASC-ECU) (Refer to Service and Repair). Then go to Step 12.
NO The procedure is complete.
STEP 12. Check whether the DTC is reset.
(1)Erase the DTC.
(2)Drive the vehicle at 12 mph (20 km/h) or higher.
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 C101C set?
YES Return to Step 1.
NO The procedure is complete.