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Home › Lexus › 2008 › LS 460 › Repair and Diagnosis › Accessories & Equipment › Cruise Control Systems › Cruise Control › Cruise Control System › DTC P0571: Stop Light Switch Circuit Malfunction › Inspection Procedure

Inspection Procedure

  1. READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH) 
    1. Check the Data List for proper functioning of the stop light switch.

      Cruise Control 

    DATA LIST TABLE

    Tester Display Measurement Item/Range Normal Condition Diagnostic Note
    Stop Light SW M-CPU Stop light switch signal (Main CPU) / ON or OFF OK: Brake pedal is depressed
    OFF: Brake pedal is released    		 -

    OK: Display changes according to brake pedal operation described in the above table. 

    NG:  Go to step  2

    OK: REPLACE ECM  (See REMOVAL )

  2. INSPECT FUSE (STOP, ECU-IG) 
    1. Remove the STOP fuse from the main body ECU.
    2. Remove the ECU-IG fuse from the engine room No. 2 junction block.
    3. Measure the resistance of the fuses.

      Standard resistance 

    RESISTANCE SPECIFICATION TABLE

    Tester Connection Condition Switch Condition
    STOP fuse Always Below 1 Ω
    ECU-IG fuse Always Below 1 Ω

    NG: REPLACE FUSE 

    OK: Go to Next Step 

  3. INSPECT STOP LIGHT SWITCH ASSEMBLY 
    1. Remove the stop light switch (see REMOVAL ).
    2. Measure the resistance according to the value(s) in the table below.

      Standard resistance 

      Fig 1: Identifying Stop Light Switch Assembly
      G04951393Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    RESISTANCE SPECIFICATION TABLE

    Tester Connection Switch Condition Specified Condition
    1 - 2 Pushed Below 1 Ω
    1 - 2 Not pushed 10 kΩ or higher
    3 - 4 Not pushed Below 1 Ω
    3 - 4 Pushed 10 kΩ or higher

    NG: REPLACE STOP LIGHT SWITCH ASSEMBLY  (See REMOVAL )

    OK: Go to Next Step 

  4. CHECK HARNESS AND CONNECTOR (ECM - BATTERY) 
    1. Disconnect the A14 ECM connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard voltage 

      Fig 2: Identifying A14 ECM Connector
      G04951394Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    VOLTAGE SPECIFICATION TABLE

    Tester Connection Switch Condition Specified Condition
    A14-12 (STP) - Body ground Brake pedal is depressed 11 to 14 V
    A14-12 (STP) - Body ground Brake pedal is released Below 1 V
    A14-13 (ST1-) - Body ground Brake pedal is released 11 to 14 V
    A14-13 (ST1-) - Body ground Brake pedal is depressed Below 1 V

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: REPLACE ECM  (See REMOVAL )

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