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Home >> Lexus >> 2020 >> LS 500 Base, AWD >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Electronically Controlled Brake System (W/ Vacuum Brake Booster) - Diagnostic Codes (3 Of 4) >> ELECTRONICALLY CONTROLLED BRAKE SYSTEM (w/ Vacuum Brake Booster) >> DTC C1427: Motor Malfunction [12/2017 - 09/2018] >> Procedure

DTC C1427: Motor Malfunction [12/2017 - 09/2018]: Procedure

  1. PERFORM ACTIVE TEST USING TECHSTREAM (MOTOR RELAY) 
    1. Connect the Techstream to the DLC3.
    2. Start the engine.
    3. Select the Active Test using the Techstream.

      Refer to DATA LIST / ACTIVE TEST [12/2017 - 09/2018]

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display Measurement Item Control Range Diagnostic Note
      Motor Relay Motor relay Relay ON/OFF Operating sound of motor can be heard

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display
      Motor Relay
    4. Check the operating sound of the pump motor when operating it using the Techstream.

      Result

      Result Proceed to
      Operating sound is not heard. A
      Operating sound is heard. B

    Result: 

    B 

    See step  4

    Result: 

    A 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (GND2 TERMINAL) 
    1. Turn the engine switch off.
    2. Make sure that there is no looseness at the locking part and the connecting part of the connectors.
    3. Disconnect the A9 skid control ECU (brake actuator assembly) connector.
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A9-1 (GND2) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (GND2 CIRCUIT) 

    Result: 

    OK 

    See step  3

  3. RECONFIRM DTC 

    HINT: 

    The motor relay is in the skid control ECU (brake actuator assembly). Therefore, motor relay unit inspection cannot be performed. Be sure to check if the DTC is output before replacing the skid control ECU (brake actuator assembly).

    1. Reconnect the A9 skid control ECU (brake actuator assembly) connector.
    2. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [12/2017 - 09/2018]

      Chassis > ABS/VSC/TRAC > Clear DTCs 

    3. Turn the engine switch off.
    4. Start the engine.
    5. Perform a road test.
    6. Check if the same DTC is output.

      Refer to DTC CHECK / CLEAR [12/2017 - 09/2018]

      Chassis > ABS/VSC/TRAC > Trouble Codes 

      Result

      Result Proceed to
      DTC C1427 is not output. A
      DTC C1427 is output. B

      HINT: 

      • If a speed signal of 6 km/h (4 mph) or more is input to the skid control ECU (brake actuator assembly) with the engine switch on (IG) and the stop light switch assembly off, the ECU performs self diagnosis of the pump motor circuit.
      • If the normal system code is output (no DTCs are output), slightly jiggle the connectors, wire harness, and fuses of the skid control ECU (brake actuator assembly).
      • If any DTCs are output while jiggling a connector or wire harness of the skid control ECU (brake actuator assembly), inspect and repair the connector or wire harness.
      • If no DTCs were output when reconfirming DTCs, checking for intermittent problems is necessary because it is suspected that the original DTCs were stored due to the poor connection of a connector terminal.

    Result: 

    A 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [12/2017 - 09/2018] 

    Result: 

    B 

    REPLACE BRAKE ACTUATOR ASSEMBLY. Refer to  REMOVAL [12/2017 - 09/2018] 

  4. RECONFIRM DTC 

    HINT: 

    The motor relay is in the skid control ECU (brake actuator assembly). Therefore, motor relay unit inspection cannot be performed. Be sure to check if the DTC is output before replacing the skid control ECU (brake actuator assembly).

    1. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [12/2017 - 09/2018]

      Chassis > ABS/VSC/TRAC > Clear DTCs 

    2. Turn the engine switch off.
    3. Start the engine.
    4. Perform a road test.
    5. Check if the same DTC is output.

      Refer to DTC CHECK / CLEAR [12/2017 - 09/2018]

      Chassis > ABS/VSC/TRAC > Trouble Codes 

      Result

      Result Proceed to
      DTC C1427 is not output. A
      DTC C1427 is output. B

      HINT: 

      • If a speed signal of 6 km/h (4 mph) or more is input to the skid control ECU (brake actuator assembly) with the engine switch on (IG) and the stop light switch assembly off, the ECU performs self diagnosis of the pump motor circuit.
      • If the normal system code is output (no DTCs are output), slightly jiggle the connectors, wire harness, and fuses of the skid control ECU (brake actuator assembly).
      • If any DTCs are output while jiggling a connector or wire harness of the skid control ECU (brake actuator assembly), inspect and repair the connector or wire harness.
      • If no DTCs were output when reconfirming DTCs, checking for intermittent problems is necessary because it is suspected that the original DTCs were stored due to the poor connection of a connector terminal.

    Result: 

    A 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [12/2017 - 09/2018] 

    Result: 

    B 

    REPLACE BRAKE ACTUATOR ASSEMBLY. Refer to  REMOVAL [12/2017 - 09/2018] 

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