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Home >> Lexus >> 2023 >> LX 600 Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System (W/O Canister Pump Module) - Diagnostic Codes (4 Of 5) >> SFI SYSTEM (w/o Canister Pump Module) >> DTC P0504-2B: Brake Switch "A"/"B" Signal Cross Coupled [12/2021 - ] >> Procedure
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DTC P0504-2B: Brake Switch "A"/"B" Signal Cross Coupled [12/2021 - ]: Procedure

  1. CHECK TERMINAL VOLTAGE (POWER SOURCE OF STOP LIGHT SWITCH ASSEMBLY) 

    Pre-procedure1

    1. Disconnect the stop light switch assembly connector.

      Procedure1

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      B87-1 (B) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    3. None

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BATTERY) 

    Result: 

    OK 

    See step  2

  2. CHECK TERMINAL VOLTAGE (POWER SOURCE OF STOP LIGHT SWITCH ASSEMBLY) 

    Pre-procedure1

    1. Disconnect the stop light switch assembly connector.
    2. Turn the ignition switch to ON.

      Procedure1

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      B87-5 (B) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    4. None

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - IGP NO. 1 RELAY) 

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BODY GROUND) 

    Pre-procedure1

    1. Disconnect the stop light switch assembly connector.

      Procedure1

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      B87-3 (GND) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    3. None

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. CHECK TERMINAL VOLTAGE (STP AND ST1- VOLTAGE) 

    Pre-procedure1

    GTY809790Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Brake Pedal Depressed
    *b Brake Pedal Released
    1. Disconnect the ECM connector.
    2. Turn the ignition switch to ON.

      Procedure1

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

      Standard Voltage

      Tester Connection Brake Pedal Operation Specified Condition
      B70-21 (ST1-) - Body ground Released 7.5 to 14 V
      Depressed Below 1.5 V
      B70-22 (STP) - Body ground Released Below 1.5 V
      Depressed 7.5 to 14 V

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    4. None

    Result: 

    OK 

    REPLACE ECM. Refer to  REMOVAL [12/2021 - ] 

    Result: 

    NG 

    See step  5

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

    Pre-procedure1

    1. Disconnect the stop light switch assembly connector.
    2. Disconnect the ECM connector.

      Procedure1

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      B87-4 (L) - B70-21 (ST1-) Always Below 1 Ω
      B87-2 (L) - B70-22 (STP) Always Below 1 Ω
      B87-4 (L) or B70-21 (ST1-) - Body ground and other terminals Always 10 kΩ or higher
      B87-2 (L) or B70-22 (STP) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

      Post-procedure1

    4. None

    Result: 

    OK 

    REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  REMOVAL [12/2021 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - ECM) 

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