Code No. C121A Steering angle sensor initialization

caution

If there is any problem in the CAN bus lines, an incorrect DTC may be stored. 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 scan tool. 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.

DTC SET CONDITIONS

This DTC is stored 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

STEP 1. Scan tool (M.U.T.-III) CAN bus diagnostics

Use scan tool (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. DTC recheck after resetting CAN bus lines

Q. Is DTC No.C121A stored?

	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 DTC is stored again.

Erase the DTC.

Q. Is DTC No.C121A stored?

	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 DTC is stored again.

Erase the DTC.

Q. Is DTC No.C121A stored?

	Return to Step 1.

	This diagnosis is complete.