Inspection Procedure 8: ASC OFF display 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 lines. 

   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  10.
2. STEP 2. Using scan tool MB991958, check the DTC 

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

   Q: Is the DTC set? 

   1. YES:  Carry out the diagnosis for the DTC. (Refer to DIAGNOSTIC TROUBLE CODE CHART  .)
   2. NO:  Go to Step 3.
3. STEP 3. Actuator test of combination meter 

   Perform the following actuator test by the combination meter system, and check if the ASC OFF display or light illuminates normally. (Refer to ACTUATOR TEST TABLE <Vehicles without color liquid crystal display> or ACTUATOR TEST TABLE <Vehicles with color liquid crystal display>.)

   • Item No. 7: Indicator 1

     Q: Is the check result normal? 

     1. YES:  Go to Step 4.
     2. NO:  Replace the combination meter. (Refer to COMBINATION METER .) Then go to Step  9.
4. STEP 4. ASC OFF switch check 

   Refer to ASC OFF SWITCH CONTINUITY CHECK  .

   Q: Is the check result normal? 

   1. YES:  Go to Step 5.
   2. NO:  Replace ASC OFF switch. (Refer to ASC OFF SWITCH  .) Then go to Step  10.
5. STEP 5. Connector check: C-313 ETACS-ECU connector, C-36 intermediate connector, C-45 ASC OFF switch connector 

   Q: Is the check result normal? 

   1. YES:  Go to Step 6.
   2. NO:  Repair the damaged connector.
6. STEP 6. Wiring harness check between C-313 ETACS-ECU connector terminal No. 15 and C-45 ASC OFF switch connector terminal No. 1 
   • Check the power supply circuit for short circuit.

     Q: Is the check result normal? 

     1. YES:  Go to Step 7.
     2. NO:  Repair the wiring harness between C-313 ETACS-ECU connector terminal No. 15 and C-45 ASC OFF switch connector terminal No. 1.
7. STEP 7. Using scan tool MB991958, check the DTC for other systems 

   Using scan tool, check that DTC U0141 is not set by the combination meter system.

   Q: Is the DTC set? 

   1. YES:  Diagnose the combination meter. (Refer to TROUBLESHOOTING .) Then go to Step  10.
   2. NO:  Go to Step 8.
8. STEP 8. Using scan tool MB991958, check the DTC for other systems 

   Using scan tool, check that DTC U0121 is not set by the ETACS system.

   Q: Is the DTC set? 

   1. YES:  Perform troubleshooting on ETACS-ECU. (Refer to TROUBLESHOOTING .) Then go to Step 9.
   2. NO:  Go to Step 9.
9. STEP 9. Retest the system. 

   Q: Does ASC OFF display turn OFF normally? 

   1. YES:  Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION .)
   2. NO:  Replace the hydraulic unit (integrated with ASC-ECU). (Refer to HYDRAULIC UNIT  .) Then go to Step 10.
10. STEP 10. Retest the system. 

    Q: Does ASC OFF display turn OFF normally? 

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