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DTC C121A: Steering Wheel Sensor System (Neutral Learning Abnormality)


caution
  • If there is any problem in the CAN bus lines, an incorrect 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 steering wheel sensor is replaced, calibrate the steering wheel sensor (Refer to GROUP 35C - On-vehicle Service ), and initialise the steering angle correction amount stored in AWC-ECU. (Item No.1: Steering angle correction amount initialisation ).

OPERATION


Steering wheel sensor stores the neutral position learned by the scan tool. When the neutral position has not been learned, the steering wheel sensor outputs the signal indicating that the learning has not been performed.

DTC SET CONDITIONS


This DTC is set when it is detected that the steering wheel sensor has not learned the neutral position.

PROBABLE CAUSES



DIAGNOSTIC PROCEDURE

STEP 1. Scan tool CAN bus diagnostics
Using scan tool MB991958, 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 ). After repairing the CAN bus line, go to Step 2.

STEP 2. Check whether the DTC is reset.

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

STEP 3. Steering wheel sensor calibration.
Perform calibration of the steering wheel sensor. (Refer to GROUP 35C - On-vehicle Service ).

Q. Has the calibration succeeded?
Go to Step 4.
Replace the steering wheel sensor. (Refer to GROUP 35C - Steering Wheel Sensor ). Then, go to Step 4.

STEP 4. Check whether the DTC is reset.

Q. Is DTC No. C121A set?
Replace the AWC-ECU. (Refer to ). Then, go to Step 5.
Intermittent malfunction. (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

STEP 5. Check whether the DTC is reset.

Q. Is DTC No. C121A set?
Return to Step 1.
This diagnosis is complete.