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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 DTC 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 reset the steering wheel sensor correction amount set in the AWC-ECU (Item No. 1: Steering angle adjusted value ).
 
 
OPERATION
Steering wheel sensor stores the neutral position learned by the scan tool (M.U.T.-IIISE). 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

 
 
DIAGNOSIS
STEP 1. Scan tool (M.U.T.-IIISE) CAN bus diagnostics.
Use scan tool (M.U.T.-IIISE) to perform the CAN bus diagnosis.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - Diagnosis, Can Bus Diagnostics Table ).
 
STEP 2. Steering wheel sensor calibration.
Perform calibration of the steering wheel sensor (Refer to GROUP 35C - On-vehicle Service ).
Has the calibration succeeded?
Go to Step 3.
Replace the steering wheel sensor (Refer to GROUP 35C - Steering Wheel Sensor ).
 
STEP 3. Check whether the DTC is set again.
Is the DTC C121A set?
Replace the AWC-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).