Super All Wheel Control

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, and initialize the steering angle correction amount stored in AWC-ECU. (item No.09: Steering angle correction amount initialization.)

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
^ Steering wheel sensor neutral point not learned
^ Malfunction of steering wheel sensor
^ Malfunction of AWC ECU

DIAGNOSTIC PROCEDURE

STEP 1. Scan tool CAN bus diagnostics
Using scan tool MB991958, diagnose the CAN bus lines.

Q: Is the check result normal?
YES: Go to Step 3.
NO: Repair the CAN bus lines. After repairing the CAN bus line, go to Step 2.

STEP 2. Check whether the DTC is reset.

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

STEP 3. Steering wheel sensor calibration
Perform calibration of the steering wheel sensor.

Q: Has the calibration succeeded?
YES: Go to Step 4.
NO: Replace the steering wheel sensor. Then, go to Step 4.

STEP 4. Check whether the DTC is reset.

Q: Is DTC No. C121A set?
YES: Replace the AWC-ECU. Then, go to Step 5.
NO: Intermittent malfunction.

STEP 5. Check whether the DTC is reset.

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