Code No. C121A Abnormality in steering wheel sensor initialisation


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, Trouble code diagnosis ).

OPERATION
Steering wheel sensor stores the neutral position learned by M.U.T.-III. When the neutral position has not been stored in the steering wheel sensor yet, the steering wheel sensor outputs the signal indicating that it does not have neutral position.

DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set when ASC-ECU detects that the steering wheel sensor has not learned the neutral position yet.

PROBABLE CAUSES

  • Steering wheel sensor malfunction
  • ASC-ECU malfunction
  • Neutral position of steering wheel sensor not learned

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 - Troubleshooting ). On completion, go to Step 2.

STEP 2. Diagnosis code recheck after resetting CAN bus lines

Q. Is the diagnosis code No. C121A set?
Go to Step 3.
This diagnosis is complete.

STEP 3. Steering wheel sensor calibration
Perform calibration of steering wheel sensor (Refer to ).

Q. Has the calibration succeeded?
Go to Step 4.
Replace the steering wheel sensor, and then go to Step 4.

STEP 4. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. C121A set?
Replace the ASC-ECU.
This diagnosis is complete.