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Home >> Lexus >> 2024 >> GX 550 Overtrail >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Electronically Controlled Brake System - Diagnostic Codes (2 Of 2) & Symptom Tests >> Electronically Controlled Brake System >> DTC P0571-11: Brake Switch "A" Circuit Short to Ground [12/2023 - ] >> Procedure

DTC P0571-11: Brake Switch "A" Circuit Short to Ground [12/2023 - ]: Procedure

  1. CHECK BRAKE PEDAL HEIGHT AND STOP LIGHT SWITCH ASSEMBLY INSTALLATION 
    1. Check the brake pedal height and stop light switch assembly installation.

      HINT: 

      Refer to ADJUSTMENT [12/2023 - ]

      OK

      The brake pedal height and stop light switch assembly installation is normal.

      HINT: 

      If the on/off status of the stop light switch assembly and the pressure increase information from the master cylinder pressure sensor do not match due to an improperly installed brake pedal or stop light switch assembly, this DTC may be stored. Therefore, be sure to check the installation condition of the pedal and stop light switch assembly before inspecting the input signals and other related parts.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    ADJUST BRAKE PEDAL HEIGHT OR STOP LIGHT SWITCH ASSEMBLY INSTALLATION. Refer to  ADJUSTMENT [12/2023 - ] 

    Result: 

    OK 

    See step  2

  2. CHECK STOP LIGHT OPERATION 
    1. Check that the stop lights come on when the brake pedal is depressed, and go off when the brake pedal is released.

      OK

      Condition Illumination Condition
      Brake pedal depressed. On
      Brake pedal released. Off

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  11

    Result: 

    OK 

    See step  3

  3. READ VALUE USING GTS (STOP LIGHT SW) 

    Pre-procedure1

    1. Connect the GTS to the DLC3.
    2. Turn the ignition switch to ON.

      Procedure1

    3. Enter the following menus: Chassis / Brake/EPB / Data List.

      Chassis > Brake/EPB > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Stop Light SW light switch assembly status
      (STP or STP2 terminal input)      		 OFF / ON OFF: Brake pedal released
      ON: Brake pedal depressed      		 HINT: 
      • Stop light control relay off: STP terminal status displayed.
      • Stop light control relay on: STP2 terminal status displayed.
      Brake Pedal Load Sensing SW Brake pedal load sensing switch OFF / ON OFF: Brake pedal released
      ON: Brake pedal depressed      		 -

      Chassis > Brake/EPB > Data List 

      Tester Display
      Stop Light SW
      Brake Pedal Load Sensing SW
    4. Check that the stop light switch display and brake pedal load sensing switch display observed on the GTS change according to brake pedal operation.

      OK

      The GTS displays OFF / ON according to brake pedal operation.

      Procedure2

    5. Slowly depress the brake pedal, and check when the stop light switch assembly and brake pedal load sensing switch turn on.

      OK

      First the stop light switch assembly should turn on, and then the brake pedal load sensing switch should turn on.

      Result

      Result Proceed to
      OK A
      NG (The stop light switch assembly does not turn on.) B
      NG (Turning on of the brake pedal load sensing switch is not confirmed.) C
      NG (The brake pedal load sensing switch turns on first.) D

      Post-procedure1

    6. None

    Result: 

    B 

    See step  6

    Result: 

    C 

    See step  10

    Result: 

    D 

    REPLACE BRAKE PEDAL SUPPORT ASSEMBLY. Refer to  REMOVAL [12/2023 - ] 

    Result: 

    A 

    See step  4

  4. CLEAR DTC 

    Pre-procedure1

    1. None

      Procedure1

    2. Operate the GTS to clear the codes. Enter the following menus: Chassis / Brake/EPB / Trouble Codes.

      Chassis > Brake/EPB > Clear DTCs 

      Result

      Proceed to
      NEXT

      Post-procedure1

    3. Press the DTC clear button.
    4. Turn the ignition switch off.

    Result: 

    NEXT 

    See step  5

  5. RECONFIRM DTC 

    Pre-procedure1

    1. Start the engine.
    2. Perform a road test.

      Procedure1

    3. Read the DTCs following the prompts on the GTS. Enter the following menus: Chassis / Brake/EPB / Trouble Codes.

      Chassis > Brake/EPB > Trouble Codes 

    4. Check if the same DTC is output.

      Result

      Result Proceed to
      P0571-11 is not output A
      P0571-11 is output B

      Post-procedure1

    5. None

    Result: 

    A 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [12/2023 - ] 

    Result: 

    B 

    REPLACE BRAKE ACTUATOR ASSEMBLY. Refer to  REMOVAL [12/2023 - ] 

  6. CHECK HARNESS AND CONNECTOR (STP TERMINAL) 

    Pre-procedure1

    1. Turn the ignition switch off.

      Procedure1

    2. Make sure that there is no looseness at the locking part and the connecting part of the connectors.

      OK

      The connector is securely connected.

      Pre-procedure2

    3. Disconnect the A25 skid control ECU (brake actuator assembly) connector.

      Procedure2

    4. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

      Procedure3

    5. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A25-11 (STP) - Body ground Stop light switch assembly on (Brake pedal depressed) 8 to 14 V
      A25-11 (STP) - Body ground Stop light switch assembly off (Brake pedal released) Below 1.5 V

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    6. None

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  7

  7. CLEAR DTC 

    Pre-procedure1

    1. Reconnect the A25 skid control ECU (brake actuator assembly) connector.

      Procedure1

    2. Operate the GTS to clear the codes. Enter the following menus: Chassis / Brake/EPB / Trouble Codes.

      Chassis > Brake/EPB > Clear DTCs 

      Result

      Proceed to
      NEXT

      Post-procedure1

    3. Press the DTC clear button.
    4. Turn the ignition switch off.

    Result: 

    NEXT 

    See step  8

  8. RECONFIRM DTC 

    Pre-procedure1

    1. Start the engine.
    2. Perform a road test.

      Procedure1

    3. Read the DTCs following the prompts on the GTS. Enter the following menus: Chassis / Brake/EPB / Trouble Codes.

      Chassis > Brake/EPB > Trouble Codes 

    4. Check if the same DTC is output.

      Result

      Result Proceed to
      P0571-11 is not output A
      P0571-11 is output B

      Post-procedure1

    5. None

    Result: 

    B 

    REPLACE BRAKE ACTUATOR ASSEMBLY. Refer to  REMOVAL [12/2023 - ] 

    Result: 

    A 

    See step  9

  9. INSPECT BRAKE PEDAL SUPPORT ASSEMBLY 

    Pre-procedure1

    1. Turn the ignition switch off.

      Procedure1

    2. Inspect the brake pedal load sensing switch (brake pedal support assembly).

      Refer to ON-VEHICLE INSPECTION [12/2023 - ]

      OK

      The brake pedal load sensing switch (brake pedal support assembly) is normal.

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    3. None

    Result: 

    OK 

    See step  10

    Result: 

    NG 

    REPLACE BRAKE PEDAL SUPPORT ASSEMBLY. Refer to  REMOVAL [12/2023 - ] 

  10. CHECK HARNESS AND CONNECTOR (BRAKE PEDAL SUPPORT ASSEMBLY - BRAKE ACTUATOR ASSEMBLY) 

    Procedure1

    1. Make sure that there is no looseness at the locking part and the connecting part of the connectors.

      OK

      The connector is securely connected.

      Pre-procedure1

    2. Disconnect the A25 skid control ECU (brake actuator assembly) connector.
    3. Disconnect the A46 brake pedal load sensing switch (brake pedal support assembly) connector.

      Procedure2

    4. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

      Procedure3

    5. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A46-2 (FSW+) - A25-28 (FSW+) Always Below 1 Ω
      A46-2 (FSW+) or A25-28 (FSW+) - Body ground Always 10 kΩ or higher
      A46-1 (FSW-) - Body ground 1 minute or more after disconnecting the cable from the negative (-) battery terminal Below 1 Ω

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    6. None

    Result: 

    OK 

    REPLACE BRAKE ACTUATOR ASSEMBLY. Refer to  REMOVAL [12/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  11. INSPECT STOP LIGHT SWITCH ASSEMBLY 
    1. Inspect the stop light switch assembly.

      Refer to ON-VEHICLE INSPECTION [12/2023 - ]

      OK

      The stop light switch assembly is normal.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  REMOVAL [12/2023 - ] 

    Result: 

    OK 

    See step  12

  12. CHECK HARNESS AND CONNECTOR (STP TERMINAL) 

    Pre-procedure1

    1. Turn the ignition switch off.

      Procedure1

    2. Make sure that there is no looseness at the locking part and the connecting part of the connectors.

      OK

      The connector is securely connected.

      Pre-procedure2

    3. Disconnect the A25 skid control ECU (brake actuator assembly) connector.

      Procedure2

    4. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

      Procedure3

    5. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A25-11 (STP) - Body ground Stop light switch assembly on (Brake pedal depressed) 8 to 14 V
      A25-11 (STP) - Body ground Stop light switch assembly off (Brake pedal released) Below 1.5 V

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    6. None

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  13

  13. CLEAR DTC 

    Pre-procedure1

    1. Reconnect the A25 skid control ECU (brake actuator assembly) connector.
    2. Connect the GTS to the DLC3.
    3. Turn the ignition switch to ON.

      Procedure1

    4. Operate the GTS to clear the codes. Enter the following menus: Chassis / Brake/EPB / Trouble Codes.

      Chassis > Brake/EPB > Clear DTCs 

      Result

      Proceed to
      NEXT

      Post-procedure1

    5. Press the DTC clear button.
    6. Turn the ignition switch off.

    Result: 

    NEXT 

    See step  14

  14. RECONFIRM DTC 

    Pre-procedure1

    1. Start the engine.
    2. Perform a road test.

      Procedure1

    3. Read the DTCs following the prompts on the GTS. Enter the following menus: Chassis / Brake/EPB / Trouble Codes.

      Chassis > Brake/EPB > Trouble Codes 

    4. Check if the same DTC is output.

      Result

      Result Proceed to
      P0571-11 is not output A
      P0571-11 is output B

      Post-procedure1

    5. None

    Result: 

    A 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [12/2023 - ] 

    Result: 

    B 

    REPLACE BRAKE ACTUATOR ASSEMBLY. Refer to  REMOVAL [12/2023 - ] 

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