DTC C121A: Abnormality in steering wheel sensor initialization: Diagnosis

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Required Special Tools:

MB991958 Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827 M.U.T.-III USB Cable
- MB991910 M.U.T.-III Main Harness A

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

Q: Is the check result normal?
1. YES: Go to Step 3.
2. NO: Repair the CAN bus lines (Refer to CAN BUS DIAGNOSTICS TABLE ). After repairing the CAN bus line, go to Step 2.
STEP 2. DTC recheck after repairing the CAN bus line
Q: Is DTC C121A set?
1. YES: Go to Step 3.
2. NO: The procedure is complete.
STEP 3. Steering wheel sensor calibration
Perform calibration of the steering wheel sensor (Refer to STEERING WHEEL SENSOR CALIBRATION ).

Q: Has the calibration succeeded?
1. YES: Go to Step 4.
2. NO: Replace the steering wheel sensor (Refer to REMOVAL AND INSTALLATION ). Then go to Step 4.
STEP 4. Check whether the DTC is reset.
Erase the DTC.

Q: Is DTC C121A set?
1. YES: Replace the hydraulic unit (integrated with ASC-ECU) (Refer to HYDRAULIC UNIT ). Then go to Step 5.
2. NO: The procedure is complete.
STEP 5. Check whether the DTC is reset.
Erase the DTC.

Q: Is DTC C121A set?
1. YES: Return to Step 1.
2. NO: The procedure is complete.