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DTC U0121: CAN timeout error (ABS/ASC): Diagnosis

  1. STEP 1. M.U.T.-III CAN bus diagnostics 

    Use scan tool to perform the CAN bus diagnosis.

    Q: Is the check result normal? 

  2. STEP 2. M.U.T.-III diagnostic trouble code 

    Check if the ABS/ASC-related diagnostic trouble code is set.

    Q: Is the ABS/ASC-related diagnostic trouble code set? 

    • YES:  Carry out the appropriate troubleshooting.
    • NO:  Go to Step 3.
  3. STEP 3. M.U.T.-III diagnostic trouble code 

    Is diagnostic trouble code No. U0121 set in the other ECU, which communicates with the ABS/ASC-ECU via CAN?

    Q: Is the diagnostic trouble code set? 

    • YES:  Go to Step 4.
    • NO:  Go to  Step 5.
  4. STEP 4. Symptom recheck after erasing diagnostic trouble code 

    Q: Is the diagnostic trouble code set? 

    • YES:  Replace ABS/ASC-ECU.
    • NO:  Intermittent malfunction.
  5. STEP 5. Symptom recheck after erasing diagnostic trouble code 

    Q: Is the diagnostic trouble code set? 

    • YES:  Replace TCM.
    • NO:  Intermittent malfunction.