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Home >> Lexus >> 2025 >> NX 350h >> Repair and Diagnosis >> External Pages >> Different car >> Section 96 (Electronically Controlled Brake System - Diagnostic Codes (3 Of 3), Symptom Tests & Circuit Tests) >> ELECTRONICALLY CONTROLLED BRAKE SYSTEM (for Gasoline Model) >> DTC P0571-12: Brake Switch "A" Circuit Short to Battery [11/2021 - ] >> Procedure

DTC P0571-12: Brake Switch "A" Circuit Short to Battery [11/2021 - ]: Procedure

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

      HINT: 

      Refer to ADJUSTMENT [11/2021 - ]

      OK

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

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    ADJUST BRAKE PEDAL OR STOP LIGHT SWITCH ASSEMBLY. Refer to  ADJUSTMENT [11/2021 - ] 

    Result: 

    OK 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY OUTPUT CIRCUIT) 

    Procedure1

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

      OK

      The connector is securely connected.

      Pre-procedure1

    2. Disconnect the A36 skid control ECU (brake actuator assembly) connector.

      Procedure2

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

      OK

      No deformation or corrosion.

      Procedure3

    4. Measure the voltage according to the value(s) in the table below.
      GTY1059723Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Stop Light Switch Assembly)

      Standard Voltage

      Tester Connection Condition Specified Condition
      A37-2 (L) - Body ground Brake pedal released Below 1.5 V

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    5. None

    Result: 

    OK 

    REPLACE BRAKE ACTUATOR ASSEMBLY. Refer to  REMOVAL [11/2021 - ] 

    Result: 

    NG 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BRAKE ACTUATOR ASSEMBLY) 

    Procedure1

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

      OK

      The connector is securely connected.

      Pre-procedure1

    2. Disconnect the A36 skid control ECU (brake actuator assembly) connector.
    3. Disconnect the A37 stop light switch 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
      A37-2 (L) - Body ground Always Below 1.5 V

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    6. None

    Result: 

    OK 

    REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  REMOVAL [11/2021 - ] 

    Result: 

    NG 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - SEMICONDUCTOR POWER INTEGRATION ECU) 

    Procedure1

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

      OK

      The connector is securely connected.

      Pre-procedure1

    2. Disconnect the A36 skid control ECU (brake actuator assembly) connector.
    3. Disconnect the A37 stop light switch assembly connector.
    4. Disconnect the A77 semiconductor power integration ECU connector.

      Procedure2

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

      OK

      No deformation or corrosion.

      Procedure3

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A37-2 (L) - Body ground Always Below 1.5 V

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    7. None

    Result: 

    OK 

    REPLACE SEMICONDUCTOR POWER INTEGRATION ECU. Refer to  REMOVAL [11/2021 - ] 

    Result: 

    NG 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - ECM) 

    Procedure1

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

      OK

      The connector is securely connected.

      Pre-procedure1

    2. Disconnect the A36 skid control ECU (brake actuator assembly) connector.
    3. Disconnect the A37 stop light switch assembly connector.
    4. Disconnect the A77 semiconductor power integration ECU connector.
    5. Disconnect the A20 ECM connector. (for A25A-FKS)
    6. Disconnect the A19 ECM connector. (for T24A-FTS)

      Procedure2

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

      OK

      No deformation or corrosion.

      Procedure3

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A37-2 (L) - Body ground Always Below 1.5 V

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    9. None

    Result: 

    OK 

    REPLACE ECM 

    for A25A-FKS: Refer to REMOVAL [11/2021 - ]

    for T24A-FTS: Refer to REMOVAL [11/2021 - ]

    Result: 

    NG 

    See step  6

  6. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - TRANSMISSION FLOOR SHIFT ASSEMBLY) 

    Procedure1

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

      OK

      The connector is securely connected.

      Pre-procedure1

    2. Disconnect the A36 skid control ECU (brake actuator assembly) connector.
    3. Disconnect the A37 stop light switch assembly connector.
    4. Disconnect the A77 semiconductor power integration ECU connector.
    5. Disconnect the A20 ECM connector. (for A25A-FKS)
    6. Disconnect the A19 ECM connector. (for T24A-FTS)
    7. Disconnect the D39 shift control ECU (transmission floor shift assembly) connector.

      Procedure2

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

      OK

      No deformation or corrosion.

      Procedure3

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A37-2 (L) - Body ground Always Below 1.5 V

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    10. None

    Result: 

    OK 

    REPLACE TRANSMISSION FLOOR SHIFT ASSEMBLY 

    for UA81F: Refer to REMOVAL [11/2021 - ]

    for UB80E or UB80F: Refer to REMOVAL [11/2021 - ]

    Result: 

    NG 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - SMART KEY ECU ASSEMBLY) 

    Procedure1

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

      OK

      The connector is securely connected.

      Pre-procedure1

    2. Disconnect the A36 skid control ECU (brake actuator assembly) connector.
    3. Disconnect the A37 stop light switch assembly connector.
    4. Disconnect the A77 semiconductor power integration ECU connector.
    5. Disconnect the A20 ECM connector. (for A25A-FKS)
    6. Disconnect the A19 ECM connector. (for T24A-FTS)
    7. Disconnect the D39 shift control ECU (transmission floor shift assembly) connector.
    8. Disconnect the A10 certification ECU (smart key ECU assembly) connector.

      Procedure2

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

      OK

      No deformation or corrosion.

      Procedure3

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A37-2 (L) - Body ground Always Below 1.5 V

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    11. None

    Result: 

    OK 

    REPLACE SMART KEY ECU ASSEMBLY. Refer to  REMOVAL [11/2021 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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