Inspection Procedure 5: ABS warning light stays ON after the engine is started: 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 line. 

   Use scan tool to 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 CAN BUS DIAGNOSTICS TABLE ). Then go to  Step 6.
2. STEP 2. Scan tool DTC 

   Use scan tool to check the DTC for the ABS system.

   Q: Is the DTC stored? 

   1. YES:  Carry out the diagnosis for the diagnostic trouble code (Refer to DIAGNOSTIC TROUBLE CODE CHART  ).
   2. NO:  Go to Step 3.
3. STEP 3. Scan tool other system DTC 

   Using scan tool, check that DTC U0141 is not stored in the combination meter system.

   Q: Is any DTC stored? 

   1. YES:  Troubleshoot the combination meter (Refer to Combination Meter - DTC U0141: ETACS CAN TIMEOUT ), and then go to  Step 6.
   2. NO:  Go to Step 4.
4. STEP 4. Scan tool other system DTC 

   Using scan tool, check that DTC U0121 is not stored in the ETACS system.

   Q: Is any DTC stored? 

   1. YES:  Perform troubleshooting on ETACS-ECU. (Refer to ETACS - DTC U0121: ASC-ECU CAN TIMEOUT ). Then go to  Step 6.
   2. NO:  Go to Step 5.
5. STEP 5. Retest the system. 

   Drive the vehicle more at 6 mph (10 km/h) or high.

   Q: Does the ABS warning light turn ON and OFF normally? 

   1. YES:  Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
   2. NO:  Replace the hydraulic unit (integrated with ABS-ECU) (Refer to HYDRAULIC UNIT  ). Then go to Step 6.
6. STEP 6. Retest the system. 

   Drive the vehicle more at 6 mph (10 km/h) or high.

   Q: Does the ABS warning light turn ON and OFF normally? 

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