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DTC C121A Steering angle sensor initialization
 
 
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 (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 set when ASC-ECU detects that the steering wheel sensor has not learned the neutral position yet.
 
 
 
TROUBLESHOOTING HINTS
  • Neutral position of steering wheel sensor not learned
  • Steering wheel sensor malfunction
  • ASC-ECU malfunction
 
 
 
 
DIAGNOSIS
STEP 1. Scan tool (M.U.T.-IIISE) CAN bus diagnostics,
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the Scan Tool (M.U.T.-IIISE) ."
(2) Turn on the power supply mode of the electric motor switch.
(3) Diagnose the CAN bus line.
(4) Turn off the power supply mode of the electric motor switch.
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,
Is DTC 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 ).
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 ).
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 set again.
Erase the DTC.
Is DTC No.C121A set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ).
This diagnosis is complete.