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Diagnostic Procedure

  1. STEP 1. Scan tool CAN bus diagnostics 

    Using scan tool MB991958, diagnose the CAN bus lines.

    Q: Is the check result normal? 

    1. YES:  Go to STEP 2 below.
    2. NO:  Repair the CAN bus lines. (Refer to TROUBLESHOOTING .)
  2. STEP 2. Scan tool diagnostic trouble code 

    Check the ASC diagnostic trouble code. (Refer to TROUBLESHOOTING .)

    Q: Is the DTC set? 

    1. YES:  Perform the relevant troubleshooting.
    2. NO:  Go to STEP 3 below.
  3. STEP 3. Check whether the DTC is reset. 

    Q: Is DTC No. U0121 set? 

    1. YES:  Replace the AWC-ECU. (Refer to AWC-ECU  .) Then go to STEP 4 below.
    2. NO:  Intermittent malfunction. (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION .)
  4. STEP 4. Check whether the DTC is reset. 

    Q: Is DTC No. U0121 set? 

    1. YES:  Return to  Step 1.
    2. NO:  This diagnosis is complete.
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