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Home >> Lexus >> 2024 >> TX 350 Base, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 11 (Hybrid Control System - Diagnostic Codes (1 Of 6)) >> HYBRID CONTROL SYSTEM (for PHEV Model) >> DTC P0504-2B: Brake Switch "A"/"B" Signal Cross Coupled [12/2023 - ] >> Procedure

DTC P0504-2B: Brake Switch "A"/"B" Signal Cross Coupled [12/2023 - ]: Procedure

WARNING: This page is about a different car, the 2024 Lexus TX 550h+. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK TERMINAL VOLTAGE (POWER SOURCE OF STOP LIGHT SWITCH ASSEMBLY) 

    Pre-procedure1

    • Disconnect the stop light switch assembly connector.
    • Measure the voltage according to the value(s) in the table below.
      GTY1232954Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Stop Light Switch Assembly)

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      B33-1 (B) - Body ground Always 11 to 14 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the stop light switch assembly connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE OF STOP LIGHT SWITCH ASSEMBLY) 

    Result: 

    OK 

    See step  2

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

    Pre-procedure1

    • Disconnect the stop light switch assembly connector.
    • Turn the ignition switch to ON.
    • Measure the voltage according to the value(s) in the table below.
      GTY1232955Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Stop Light Switch Assembly)

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      B33-5 (B) - Body ground Ignition switch ON 11 to 14 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Turn the ignition switch off.
    • Connect the stop light switch assembly connector.

    Result: 

    NG 

    See step  6

    Result: 

    OK 

    See step  3

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

    Pre-procedure1

    • Disconnect the stop light switch assembly connector.
    • Measure the resistance according to the value(s) in the table below.
      GTY1232950Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Stop Light Switch Assembly)

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      B33-3 (GND) - Body ground Always Below 1 Ω Ω

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the stop light switch assembly connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

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

    Pre-procedure1

    • Disconnect the hybrid vehicle control ECU assembly connector.
    • Turn the ignition switch to ON.
    • Measure the voltage according to the value(s) in the table below.
      GTY1238222Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Brake Pedal Depressed *b Brake Pedal Released
      *c Front view of wire harness connector
      (to Hybrid Vehicle Control ECU Assembly)      		 - -

      Standard Voltage

      Tester Connection Brake Pedal Operation Specified Condition Result
      B88-7 (ST1-) - Body ground Released 7.5 to 14 V V
      B88-7 (ST1-) - Body ground Depressed Below 1.5 V V
      B88-22 (STP) - Body ground Released 7.5 to 14 V V
      B88-22 (STP) - Body ground Depressed Below 1.5 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the hybrid vehicle control ECU assembly connector.

    Result: 

    OK 

    REPLACE HYBRID VEHICLE CONTROL ECU ASSEMBLY. Refer to  REMOVAL [12/2023 - ] 

    Result: 

    NG 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - HYBRID VEHICLE CONTROL ECU ASSEMBLY) 

    Pre-procedure1

    • Disconnect the stop light switch assembly connector.
    • Disconnect the hybrid vehicle control ECU assembly connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      B88-7 (ST1-) - B33-4 (L) Always Below 1 Ω Ω
      B88-22 (STP) - B33-2 (L) Always Below 1 Ω Ω
      B88-7 (ST1-) or B33-4 (L) - Body ground and other terminals Always 10 kΩ or higher kΩ
      B88-22 (STP) or B33-2 (L) - Body ground and other terminals Always 10 kΩ or higher kΩ

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Connect the hybrid vehicle control ECU assembly connector.
    • Connect the stop light switch assembly connector.

    Result: 

    OK 

    REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  REMOVAL [09/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  6. CHECK HARNESS AND CONNECTOR (IGP NO. 1 RELAY - STOP LIGHT SWITCH ASSEMBLY) 

    Pre-procedure1

    • Remove the IGP NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
    • Disconnect the stop light switch assembly connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      5 (IGP NO. 1 relay holder) - B33-5 (B) Always Below 1 Ω Ω
      5(IGP NO. 1 relay holder) or B33-5 (B) - Body ground and other terminals Always 10 kΩ or higher kΩ

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Reconnect the stop light switch assembly connector.
    • Install the IGP NO. 1 relay.

    Result: 

    OK 

    CHECK SMART ENTRY AND START SYSTEM (for Start Function). Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [09/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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