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Home >> Mitsubishi >> 2010 >> Lancer ES, Standard >> Repair and Diagnosis >> Brakes >> Traction Control >> Active Stability Control System (ASC) -- Lancer >> Diagnosis >> Diagnostic Trouble Code Procedures >> DTC C121C Torque request signal rejection >> Diagnostic Procedure

Diagnostic Procedure

  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  3.
    2. NO:  Repair the CAN bus lines (Refer to CAN BUS DIAGNOSTIC TABLE ). On completion, go to Step 2.
  2. STEP 2. DTC recheck after resetting CAN bus lines 

    Q: Is DTC C121C set? 

    1. YES:  Go to Step 3.
    2. NO:  The procedure is complete.
  3. STEP 3. Using scan tool MB991958, check the other system DTC 

    Use scan tool to check that the DTC is set in the engine control module (ECM).

    Q: Is the DTC set? 

    1. YES:  Troubleshoot the engine control module (ECM) (Refer to DIAGNOSIS FUNCTION <2.0L engine non-turbo> or DIAGNOSIS FUNCTION <2.0L engine turbo> or DIAGNOSIS FUNCTION <2.4L engine>), and then go to Step  7.
    2. NO:  Go to Step 4.
  4. STEP 4. Using scan tool MB991958, check the DTC 

    Check that DTC U1417 is set in ASC-ECU.

    Q: Is DTC U1417 set? 

    1. YES:  Troubleshoot for DTC U1417 (Refer to DTC U1417 VARIANT CODING VALUE INVALID (INCLUDES FAULTY INSTALLATION)  ). Then go to Step 5.
    2. NO:  Replace the hydraulic unit (ASC-ECU) (Refer to HYDRAULIC UNIT  ). Then go to Step  7.
  5. STEP 5. Using scan tool MB991958, check the data list 

    Check the following service data (Refer to DATA LIST REFERENCE TABLE  ).

    • Item 68: Allow ESP torque request

      Q: Is the check result normal? 

      1. YES:  Go to Step 6.
      2. NO:  Replace the engine control module (ECM) (Refer to DIAGNOSIS FUNCTION <2.0L engine non-turbo> or DIAGNOSIS FUNCTION <2.0L engine turbo> or DIAGNOSIS FUNCTION <2.4L engine>), and then go to Step  7.
  6. STEP 6. Check whether the DTC is reset. 

    Q: Is DTC C121C set? 

    1. YES:  Replace the hydraulic unit (ASC-ECU) (Refer to HYDRAULIC UNIT  ). Then go to Step 7.
    2. NO:  If the trouble symptom is resolved, an intermittent malfunction such as poorly engaged connector(s) or wiring harness is suspected (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
  7. STEP 7. Check whether the DTC is reset 

    Q: Is DTC C121C set? 

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