DTC U0251: AWC Time-Out Error (Local CAN); DTC U0440: AWC Communication Error In AWC (Local CAN); DTC U0435: AWC Signal Abnormality (Local CAN): Diagnosis

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

1. 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 TROUBLESHOOTING .) After repairing the CAN bus line, go to Step 2.
2. STEP 2. DTC recheck after repairing the CAN bus line 

   Q: Is DTC U0251, U0440 or U0435 set? 

   1. YES:  Go to Step 3.
   2. NO:  This diagnosis is complete.
3. STEP 3. Diagnostic trouble code check of other system using scan tool MB991958 

   Using scan tool MB991958, check if a diagnostic trouble code is set in AWC-ECU.

   Q: Is other DTC set? 

   1. YES:  Troubleshoot the relevant diagnostic trouble code, and then go to Step  8.
   2. NO:  Go to Step 4.
4. STEP 4. Connector check: A-05 ASC-ECU connector, C-46 AWC-ECU connector, C-47 intermediate connector 

   Q: Is the check result normal? 

   1. YES:  Go to Step 5.
   2. NO:  Repair the connector, and then go to Step  8.
5. STEP 5. Wiring harness check between A-05 ASC-ECU connector terminal No. 18 and C-46 AWC-ECU connector terminal No. 9, between A-05 ASC-ECU connector terminal No. 19 and C-46 AWC-ECU connector terminal No. 10 
   • Open or short circuit check of communication circuit

     Q: Is the check result normal? 

     1. YES:  Go to Step 6.
     2. NO:  Repair the wiring harness, and then go to Step  8.
6. STEP 6. Check whether the DTC is reset. 

   Q: Are DTC U0251, U0440, and U0435 set? 

   1. YES:  Replace the AWC-ECU. (Refer to AWC-ECU .) Then go to Step 7.
   2. NO:  Intermittent malfunction. (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION .)
7. STEP 7. Check whether the DTC is reset. 

   Q: Is DTC U0251, U0440 or U0435 set? 

   1. YES:  Replace the hydraulic unit (integrated with ASC-ECU). (Refer to HYDRAULIC UNIT  .) Then go to Step 8.
   2. NO:  The procedure is complete.
8. STEP 8. Check whether the DTC is reset. 

   Q: Is DTC U0251, U0440 or U0435 set? 

   1. YES:  Return to Step  1.
   2. NO:  The procedure is complete.