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Home >> Toyota >> 2025 >> Prius Plug-In Hybrid SE >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 6 (Hybrid Control System (HEV) - Diagnostic Codes (1 Of 4)) >> HYBRID CONTROL SYSTEM (for M20A-FXS) >> DTC P0504-2B: Brake Switch "A"/"B" Signal Cross Coupled [12/2022 - ] >> Procedure

DTC P0504-2B: Brake Switch "A"/"B" Signal Cross Coupled [12/2022 - ]: Procedure

WARNING: This page is about a different variant/trim than selected.
  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.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      A18-7 (B) - Body ground Always 11 to 14 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Reconnect the stop light switch assembly connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    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.

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      A18-6 (B) - Body ground Ignition switch ON 11 to 14 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Turn the ignition switch off.
    • Reconnect 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.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      A18-2 (GND) - Body ground Always Below 1 Ω Ω

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Reconnect the stop light switch assembly connector.

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

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

    Pre-procedure1

    • Disconnect the hybrid vehicle control ECU connector.
    • Turn the ignition switch to ON.
    • Measure the voltage according to the value(s) in the table below.
      GTY1158830Courtesy 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)      		 - -

      Standard Voltage

      Tester Connection Brake Pedal Operation Specified Condition Result
      A57-7 (ST1-) - Body ground Released 7.5 to 14 V V
      A57-7 (ST1-) - Body ground Depressed Below 1.5 V V
      A57-22 (STP) - Body ground Released Below 1.5 V V
      A57-22 (STP) - Body ground Depressed 7.5 to 14 V V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • Turn the ignition switch off.
    • Reconnect the hybrid vehicle control ECU connector.

    Result: 

    OK 

    REPLACE HYBRID VEHICLE CONTROL ECU. Refer to  REMOVAL [12/2022 - 03/2023]  , or refer to  REMOVAL [03/2023 - ] 

    Result: 

    NG 

    See step  5

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

    Pre-procedure1

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

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      A57-7 (ST1-) - A18-5 (L) Always Below 1 Ω Ω
      A57-22 (STP) - A18-3 (L) Always Below 1 Ω Ω
      A57-7 (ST1-) or A18-5 (L) - Body ground and other terminals Always 10 kΩ or higher kΩ
      A57-22 (STP) or A18-3 (L) - Body ground and other terminals Always 10 kΩ or higher kΩ

      Result

      Proceed to
      OK
      NG

    Post-procedure1

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

    Result: 

    OK 

    REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  REMOVAL [12/2022 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  6. CHECK HARNESS AND CONNECTOR (IGP RELAY - STOP LIGHT SWITCH ASSEMBLY) 

    Pre-procedure1

    • Remove the IGP 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
      3 (IGP relay holder) - A18-6 (B) Always Below 1 Ω Ω
      3 (IGP relay holder) or A18-6 (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 relay.

    Result: 

    OK 

    CHECK ECU POWER SOURCE CIRCUIT. Refer to  ECU Power Source Circuit [12/2022 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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