Diagnostic Procedure

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.
2. NO: Repair the CAN bus lines. (Refer to TROUBLESHOOTING .)
STEP 2. Scan tool diagnostic trouble code
Check the engine diagnostic trouble code. (Refer to TROUBLESHOOTING .)

Q: Is the DTC set?
1. YES: Perform the relevant troubleshooting.
2. NO: Go to Step 3.
STEP 3. Scan tool service data
Check the following service data. (Refer to SERVICE DATA REFERENCE TABLE .)
- Item No. 15: Engine speed
- Item No. 16: Engine torque (Driver request value)
  Q: Is the check result normal?
  1. YES: Intermittent malfunction. (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION .)
  2. NO: Go to Step 4.
STEP 4. Check whether the DTC is reset.
Q: Is DTC No. U0401 set?
1. YES: Replace the AWC-ECU. (Refer to AWC-ECU .) Then go to Step 5.
2. NO: Intermittent malfunction. (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION .)
STEP 5. Check whether the DTC is reset.
Q: Is DTC No. U0401 set?
1. YES: Return to Step 1.
2. NO: This diagnosis is complete.