Code No. C121A SAS initialization


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.

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

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

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
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 diagnosis code No.C121A set?
Go to Step 3
This diagnosis is complete.

STEP 3. Check how steering wheel sensor is installed.
Check that the steering wheel sensor is installed correctly (Refer to ).

Q. Is the check result normal?
Go to Step 4
Install the steering wheel sensor correctly (Refer to ), and then go to Step 4.

STEP 4. Steering wheel sensor calibration
Perform calibration of steering wheel sensor (Refer to ).

Q. Has the calibration succeeded?
Go to Step 5
After the steering wheel sensor is replaced, perform the steering wheel sensor calibration to make ASC-ECU learn the neutral point again (Refer to ). Then go to Step 5.

STEP 5. Check whether the diagnosis code is reset.
Erase the diagnosis code.

Q. Is diagnosis code No.C121A set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ), and then go to Step 6.
This diagnosis is complete.

STEP 6. Check whether the diagnosis code is reset.
Erase the diagnosis code.

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