Code No. C102A: Mutual monitoring of RL wheel speed sensor


caution
  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
  • 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 , and ).

OPERATION

  • The wheel speed sensor is a kind of a pulse generator. It consists of encoders (a plate on which north and south pole sides of the magnets are arranged alternately) for detecting the wheel speed which rotates at the same speed of the wheels and wheel speed sensors. This sensor outputs frequency pulse signals in proportion to the wheel speed.
  • The pulse signals, which the wheel speed sensor creates, are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

DIAGNOSIS CODE 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 diagnosis code.

  • 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 diagnosis code No.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 (GROUP 00 - How to Use Troubleshooting/How to Treat Past Trouble ).
  • When diagnosis code No.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 PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnosis
Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 3.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ). On completion, go to Step 2.

STEP 2. Diagnosis code recheck after resetting CAN bus lines

Q. Is the diagnosis code No.C102A set?
Go to Step 3.
This diagnosis is complete.

STEP 3. M.U.T.-III diagnosis code
Check that the diagnosis code No. C1020 is also set.

Q. Is the diagnosis code No. C1020 also set?
Perform the diagnosis for the diagnosis code No. C1020 (Refer to ).
Go to Step 4.

STEP 4. Check for wheel speed sensor <RL> installation
Check how the wheel speed sensor <RL> is installed (Disconnection of wheel speed sensor <RL>, loose mounting bolt, etc.).

Q. Is the check result normal?
Go to Step 5.
Reinstall the wheel speed sensor <RL> correctly (Refer to ). Then go to Step 5.

STEP 5. Check for wheel speed sensor <RL> output current
Refer to .

Q. Is the check result normal?
Go to Step 6.
Replace the wheel speed sensor <RL> (Refer to ). Then go to Step 9.

STEP 6. Check for wheel bearing looseness
note
  • Loose wheel bearing may increase the gap between the wheel speed sensor <RL> and the wheel speed detection magnet encoder.
  • Check the Rear wheel hub assembly <RL> (Refer to GROUP 27 - Wheel Bearing Axial Play Check ).

Q. Is the check result normal?
Go to Step 7.
Replace the rear wheel hub assembly <RL> (Refer to GROUP 27 - Rear axle hub assembly ). 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?

Go to Step 8.

NO (Adhesion of foreign materials) : Remove the foreign materials and clean the encoder so as not to disturb the magnetisation pattern on it while taking care of the magnet, magnetic substance, and magnetic attraction.

NO <Deformation> : Replace the rear wheel hub assembly <RL> (Refer to GROUP 27 - Rear axle hub assembly ). Then go to Step 10.

STEP 8. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Drive the vehicle at 20 km/h or higher.
note The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 20 km/h or higher.

Q. Is diagnosis code No. C102A set?
Replace the wheel speed sensor <RL> (Refer to ). Then go to Step 9.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).

STEP 9. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Drive the vehicle at 20 km/h or higher.
note The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 20 km/h or higher.

Q. Is diagnosis code No. C102A set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ). Then go to Step 10.
This diagnosis is complete.

STEP 10. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Drive the vehicle at 20 km/h or higher.
note The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 20 km/h or higher.

Q. Is diagnosis code No. C102A set?
Return to Step 1.
This diagnosis is complete.

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