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Home >> Lexus >> 2021 >> LC 500 2D Convertible >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Diagnostic Codes (Convertible) (5 Of 7) >> SFI System >> DTC P0504: Brake Switch "A" / "B" Correlation [07/2020 - ] >> Procedure

DTC P0504: Brake Switch "A" / "B" Correlation [07/2020 - ]: Procedure

  1. READ VALUE USING TECHSTREAM (ST1 AND STOP LIGHT SWITCH) 
    1. Connect the Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine / Data List / Gas Throttle / Stop Light Switch and ST1.

      Powertrain > Engine > Data List 

      Tester Display
      ST1
      Stop Light Switch
    5. Read the value displayed on the Techstream.

      OK

      Brake Pedal Operation Stop Light Switch ST1
      Depressed ON ON
      Released OFF OFF

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    CHECK FOR INTERMITTENT PROBLEMS. Refer to  CHECK FOR INTERMITTENT PROBLEMS [07/2020 - ] 

    Result: 

    NG 

    See step  2

  2. CHECK TERMINAL VOLTAGE (POWER SOURCE OF STOP LIGHT SWITCH ASSEMBLY) 
    GTY803480Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Front view of wire harness connector
    (to Stop Light Switch Assembly)
    1. Disconnect the stop light switch assembly connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A4-1 (B) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

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

    Result: 

    OK 

    See step  3

  3. CHECK TERMINAL VOLTAGE (POWER SOURCE OF STOP LIGHT SWITCH ASSEMBLY) 
    GTY833471Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Front view of wire harness connector
    (to Stop Light Switch Assembly)
    1. Disconnect the stop light switch assembly connector.
    2. Turn the engine switch on (IG).
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      A4-5 (B) - Body ground Engine switch on (IG) 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (JUNCTION BLOCK ASSEMBLY LH - STOP LIGHT SWITCH ASSEMBLY) 

    Result: 

    OK 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BODY GROUND) 
    1. Disconnect the stop light switch assembly connector.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A4-3 (GND) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  5

  5. CHECK TERMINAL VOLTAGE (STP AND ST1- VOLTAGE) 
    GTY823076Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Brake Pedal Depressed
    *b Brake Pedal Released
    *c Front view of wire harness connector
    (to ECM)
    1. Disconnect the ECM connector.
    2. Turn the engine switch on (IG).
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Brake Pedal Operation Specified Condition
      A58-28 (ST1-) - Body ground Released 7.5 to 14 V
      Depressed Below 1.5 V
      A58-27 (STP) - Body ground Released Below 1.5 V
      Depressed 7.5 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE ECM. Refer to  REMOVAL [07/2020 - 05/2023]  , or refer to  REMOVAL [05/2023 - ] 

    Result: 

    NG 

    See step  6

  6. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - ECM) 
    1. Disconnect the stop light switch assembly connector.
    2. Disconnect the ECM connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A4-4 (L) - A58-28 (ST1-) Always Below 1 Ω
      A4-2 (L) - A58-27 (STP) Always Below 1 Ω
      A4-4 (L) or A58-28 (ST1-) - Body ground and other terminals Always 10 kΩ or higher
      A4-2 (L) or A58-27 (STP) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  REMOVAL [07/2020 - 05/2023]  , or refer to  REMOVAL [05/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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