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Home >> Mitsubishi >> 2010 >> Lancer ES, Standard >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 25 (Active Stability Control System (ASC) -- Lancer Evolution) >> Diagnosis >> Diagnostic Trouble Code Procedures >> DTC C1027: Abnormality in RL wheel speed sensor signal >> Diagnosis

DTC C1027: Abnormality in RL wheel speed sensor signal: Diagnosis

WARNING: This page is about a different variant/trim than selected.

Required Special Tools: 

  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 CAN BUS DIAGNOSTICS TABLE ). On completion, go to Step 2.
  2. STEP 2. DTC recheck after repairing the CAN bus line 

    Q: Is DTC C1027 set? 

    1. YES:  Go to Step 3.
    2. NO:  This diagnosis is complete.
  3. STEP 3. Scan tool diagnostic trouble code 

    Check if DTC No. C1020 is also set.

    Q: Is DTC C1020 also set? 

    1. YES:  Carry out the diagnosis for DTC C1020. (Refer to DTC C100A: ABNORMALITY IN FL WHEEL SPEED SENSOR CIRCUIT  .)
    2. NO:  Go to Step 4.
  4. STEP 4. Check of wheel speed sensor installation status 

    Check the installation status of wheel speed sensor <RL> (disconnection of wheel speed sensor, looseness of mounting bolt, etc.).

    Q: Is the check result normal? 

    1. YES:  Go to Step 5.
    2. NO:  Reinstall the wheel speed sensor <RL> correctly. (Refer to WHEEL SPEED SENSOR  .) Then go to Step  16.
  5. STEP 5. Check of wheel speed sensor as a single unit 

    Refer to WHEEL SPEED SENSOR CURRENT CHECK  .

    Q: Is the check result normal? 

    1. YES:  Go to Step 6.
    2. NO:  Replace the wheel speed sensor <RL>. (Refer to WHEEL SPEED SENSOR  .) Then go to Step  16.
  6. STEP 6. Wheel bearing looseness check 
    NOTE:
    • Wheel bearing looseness may increase the gap between the wheel speed sensor and the wheel speed detection magnet encoder.
    • Check the wheel bearing <RL> for looseness. (Refer to ON-VEHICLE SERVICE .)

    Q: Is the check result normal? 

    1. YES:  Go to Step 7.
    2. NO:  Replace the rear wheel hub assembly. (Refer to REAR AXLE HUB ASSEMBLY .)
  7. STEP 7. Check of wheel speed detection encoder 

    Check the encoder for adhesion of foreign materials or deformation.

    Q: Is the check result normal? 

    1. YES:  Go to Step 8.
    2. NO (Adhesion of foreign materials):  Clean the encoder so as not to disturb the magnetization pattern on the encoder while taking care of the magnet, magnetic substance, and magnetic attraction. Then go to Step  16.
    3. NO (Deformation):  Replace the rear wheel hub assembly. (Refer to REAR AXLE HUB ASSEMBLY .) Then go to Step  16.
      Fig 1: Identifying Rear Wheel Bearing, Rear Wheel Hub Assembly And Magnetic Encoder
      G05394635Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  8. STEP 8. Voltage measurement at A-05 ASC-ECU connector 
    1. Disconnect the ASC-ECU connector, connect the special tool ASC check harness (MB991997) to the wiring harness-side connector, and then measure at the special tool connector side.
      NOTE: Do not connect the special tool to ASC-ECU.
    2. Turn the ignition switch to the ON position.
    3. Measure the voltage between the wheel speed sensor circuit power supply terminal (signal terminal) No. 36 and the body ground as well as between the ground terminal No. 37 and the body ground.

      OK: 1 volt or less 

      Q: Is the check result normal? 

      1. YES:  Go to Step 9.
      2. NO (Not normal at the terminal No. 36 or 37):  Go to Step  10.
        Fig 2: Measuring Voltage Between Wheel Speed Sensor Power Supply Terminal (Signal Terminal) No. 36 And Body Ground
        G05394617Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  9. STEP 9. Resistance measurement at A-05 ASC-ECU connector 
    1. Disconnect the ASC-ECU connector, connect the special tool ASC check harness (MB991997) to the wiring harness-side connector, and then measure at the special tool connector side.
      NOTE: Do not connect the special tool to ASC-ECU.
    2. Measure the resistance between the wheel speed sensor circuit power supply terminal (signal terminal) No. 36 and the body ground as well as between the ground terminal No. 37 and the body ground.

      OK: No continuity 

      Q: Is the check result normal? 

      1. YES:  Go to Step  12.
      2. NO (Not normal at the terminal No. 36 or 37):  Go to Step 10.
        Fig 3: Measuring Resistance Between Wheel Speed Sensor Circuit Power Supply Terminal (Signal Terminal) No. 36 And Body Ground
        G05394618Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  10. STEP 10. Connector check: A-05 ASC-ECU connector, C-45 intermediate connector, D-18 wheel speed sensor <RL> connector 

    Q: Is the check result normal? 

    1. YES:  Go to Step 11.
    2. NO:  Repair the defective connector. Then go to Step  16.
  11. STEP 11. Wiring harness check between A-05 ASC-ECU connector terminal No. 36 and D-18 wheel speed sensor <RL> connector terminal No. 1, and between A-05 ASC-ECU connector terminal No. 37 and D-18 wheel speed sensor <RL> connector terminal No. 2 
    • Check for short circuit in wheel speed sensor <RL> circuit

      Q: Is the check result normal? 

      1. YES:  Replace the wheel speed sensor <RL>. (Refer to WHEEL SPEED SENSOR  .) Then, go to Step  16.
      2. NO:  Repair the wiring harness. Then go to Step  16.
  12. STEP 12. Voltage measurement at A-05 ASC-ECU connector 
    1. Disconnect the ASC-ECU connector, connect the special tool ASC check harness (MB991997) to the ASC-ECU-side connector and the wiring harness-side connector, and then measure at the special tool connector side.
    2. Turn the ignition switch to the ON position.
    3. Measure the voltage between the wheel speed sensor circuit power supply terminal (signal terminal) No. 36 and the body ground.

      OK: Battery positive voltage 

      Q: Is the check result normal? 

      1. YES:  Go to Step 13.
      2. NO:  Go to Step  15.
        Fig 4: Measuring Voltage Between Wheel Speed Sensor Circuit Power Supply Terminal (Signal Terminal) No. 36 And Body Ground
        G05394619Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  13. STEP 13. Connector check: A-05 ASC-ECU connector, C-45 intermediate connector, D-18 wheel speed sensor <RL> connector 

    Q: Is the check result normal? 

    1. YES:  Go to Step 14.
    2. NO:  Repair the defective connector. Then go to Step  16.
  14. STEP 14. Wiring harness check between A-05 ASC-ECU connector terminal No. 36 and D-18 wheel speed sensor <RL> connector terminal No. 1, and between A-05 ASC-ECU connector terminal No. 37 and D-18 wheel speed sensor <RL> connector terminal No. 2 
    • Open circuit check of wheel speed sensor <RL> circuit

      Q: Is the check result normal? 

      1. YES:  Go to Step 15.
      2. NO:  Repair the wiring harness. Then go to Step  16.
  15. STEP 15. Check whether the DTC is reset. 
    1. Erase the DTC.
    2. Drive the vehicle at 12mph (20 km/h) or more.
      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 C1027 set? 

      1. YES:  Replace the hydraulic unit (incorporates in ASC-ECU). (Refer to HYDRAULIC UNIT  .) Then go to Step 16.
      2. NO:  Intermittent malfunction. (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION .)
  16. STEP 16. Check whether the DTC is reset. 
    1. Erase the DTC.
    2. Drive the vehicle at 12mph (20 km/h) or more.
      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 C1027 set? 

      1. YES:  Return to Step  1.
      2. NO:  This diagnosis is complete.
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