DTC C1020: Abnormality in RL wheel speed sensor circuit: 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
• MB991974: ABS check harness

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 DIAGNOSTICS TABLE ). On completion, go to Step 2.
2. STEP 2. DTC recheck after resetting CAN bus lines 

   Q: Is the DTC C1020 set? 

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

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

   • Item No. 03: RL wheel speed sensor

   Q: Is the check result normal? 

   1. YES:  Go to  Step 12.
   2. NO:  Go to Step 4.
4. STEP 4. Voltage measurement at the A-03 ABS-ECU connector 
   1. Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) to the harness-side connector, and then measure the voltage at the special tool connector side.
      NOTE: Do not connect the special tool to ABS-ECU.
   2. Turn the ignition switch to the ON position.
   3. Measure the voltage between the rear wheel speed sensor (LH) power supply terminal (signal terminal) No. 24 and body ground, and between the ground terminal No. 25 and body ground.

      OK: 1 V or less 

   Q: Is the check result normal? 

   1. YES:  Go to Step 5.
   2. NO:  (Not normal at the terminal No. 24 or 25): Go to  Step 6.
      Fig 1: Measuring Voltage Between Terminal No. 24 And Body Ground

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
5. STEP 5. Resistance measurement at A-03 ABS-ECU connector 
   1. Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) to the harness-side connector, and then measure the resistance at the special tool connector side.
      NOTE: Do not connect the special tool to ABS-ECU.
   2. Measure the resistance between the rear wheel speed sensor (LH) power supply terminal (signal terminal) No. 24 and body ground, and between the ground terminal No. 25 and body ground.

      OK: No continuity 

   Q: Is the check result normal? 

   1. YES:  Go to  Step 8.
   2. NO:  (Not normal at the terminal No. 24 or 25): Go to Step 6.
      Fig 2: Measuring Resistance Between Terminal No. 24 And Body Ground

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
6. STEP 6. Connector check: A-03 ABS-ECU connector, C-39 and D-15 intermediate connector, F-21 rear wheel speed sensor (LH) connector 

   Q: Is the check result normal? 

   1. YES:  Go to Step 7.
   2. NO:  Repair the defective connector. Then go to  Step 13.
7. STEP 7. Wiring harness check between A-03 ABS-ECU connector terminal No. 24 and F-21 rear wheel speed sensor (LH) connector terminal No. 1, and between A-03 ABS-ECU connector terminal No. 25 and F-21 rear wheel speed sensor (LH) connector terminal No. 2. 
   • Check for short circuit in rear wheel speed sensor (LH) circuit

   Q: Is the check result normal? 

   1. YES:  Replace the wheel speed sensor < RL > (Refer to WHEEL SPEED SENSOR  ). Then go to  Step 13.
   2. NO:  Repair the wiring harness. Then go to  Step 13.
8. STEP 8. Voltage measurement at the A-03 ABS-ECU connector 
   1. Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) to the ABS-ECU-side connector and harness-side connector, and then measure the voltage at the special tool connector side.
   2. Turn the ignition switch to the ON position.
   3. Measure the voltage between the rear wheel speed sensor (LH) power supply terminal (signal terminal) No. 24 and body ground, and between the ground terminal No. 25 and body ground.

      OK: 

      Terminal No. 24 and body ground: Battery positive voltage 

      Terminal No. 25 and body ground: 1 V or less 

   Q: Is the check result normal? 

   1. YES:  Go to Step 9.
   2. NO:  Go to  Step 11.
      Fig 3: Measuring Voltage Between Terminal No. 24 And Body Ground

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
9. STEP 9. Wiring harness check between A-03 ABS-ECU connector terminal No. 24 and F-21 rear wheel speed sensor (LH) connector terminal No. 1, and between A-03 ABS-ECU connector terminal No. 25 and F-21 rear wheel speed sensor (LH) connector terminal No. 2. 
   • Check for open circuit in rear wheel speed sensor (LH) circuit

   Q: Is the check result normal? 

   1. YES:  Go to Step 10.
   2. NO:  Repair the wiring harness. Then go to  Step 13.
10. STEP 10. Check for wheel speed sensor < RL > as a single unit 

    Refer to WHEEL SPEED SENSOR CURRENT CHECK  .

    Q: Is the check result normal? 

    1. YES:  Go to Step 11.
    2. NO:  Replace the wheel speed sensor < RL > (Refer to WHEEL SPEED SENSOR  ). Then go to  Step 13.
11. STEP 11. Connector check: A-03 ABS-ECU connector, C-39 and D-15 intermediate connector, F-21 rear wheel speed sensor (LH) connector 

    Q: Is the check result normal? 

    1. YES:  Go to Step 12.
    2. NO:  Repair the defective connector. Then go to  Step 13.
12. STEP 12. Check whether the DTC is reset. 
    1. Erase the DTC.
    2. Drive the vehicle at 12mph (20 km/h) or higher.
       NOTE: The ABS warning light does not turn OFF in some cases unless the vehicle runs at 12mph (20 km/h) or higher.

    Q: Is DTC C1020 set? 

    1. YES:  Replace the hydraulic unit (integrated with ABC-ECU) (Refer to HYDRAULIC UNIT  ). Then go to Step 13.
    2. NO:  Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTIONS ).
13. STEP 13. Check whether the DTC is reset. 
    1. Erase the DTC.
    2. Drive the vehicle at 12mph (20 km/h) or higher.
       NOTE: The ABS warning light does not turn OFF in some cases unless the vehicle runs at 12mph (20 km/h) or higher.

    Q: Is DTC C1020 set? 

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