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Home >> Lexus >> 2008 >> LX 570 >> Repair and Diagnosis >> Accessories & Equipment >> Cruise Control Systems >> Cruise Control >> Dynamic Radar Cruise Control System >> DTC P0571: Stop Light Switch Circuit Malfunction >> Inspection Procedure

Inspection Procedure

  1. INSPECT FUSE (STOP, IGN, ECU-IG No. 2) 
    1. Remove the STOP and IGN fuses from the engine room relay block.
    2. Remove the ECU-IG No. 2 fuse from the cowl side junction block LH.

      Standard Resistance 

      STANDARD RESISTANCE SPECIFICATION

      Tester Connection Condition Specified Condition
      STOP fuse Always Below 1 Ω
      IGN fuse
      ECU-IG No. 2 fuse

    NG: REPLACE FUSE 

    OK: Go to next step 

  2. READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH) 
    1. Using the Techstream, read the Data List.

      Radar Cruise 

      DATA LIST - RADAR CRUISE

      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Stop Light SW M-CPU Stop light switch signal (Main CPU)/ ON or OFF ON: Brake pedal depressed
      OFF: Brake pedal released      		 -
      Stop Light SW-1 S-CPU Stop light switch signal (Sub CPU)/ ON or OFF ON: Brake pedal depressed
      OFF: Brake pedal released      		 -
      Stp Light SW S2-CPU Stop light switch signal (Sub CPU)/ ON or OFF ON: Brake pedal depressed
      OFF: Brake pedal released      		 -

      OK: Normal conditions listed above are displayed. 

    NG:  Go to step  10

    OK: Go to next step 

  3. INSPECT BRAKE LIGHT RELAY (BRK LP) 
    1. Remove the brake light relay from the engine room relay block.
    2. Measure the resistance according to the value(s) in the table below.
      Fig 1: Inspecting Brake Light Relay (BRK LP)
      G05760390Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Resistance 

      STANDARD RESISTANCE SPECIFICATION

      Tester Connection Condition Specified Condition
      3-4 Battery voltage is applied to terminals 1 and 2 10 kΩ higher
      Battery voltage is not applied to terminals 1 and 2 Below 1 Ω
      3-5 Battery voltage is not applied to terminals 1 and 2 10 kΩ higher
      Battery voltage is applied to terminals 1 and 2 Below 1 Ω

    NG: REPLACE BRAKE LIGHT RELAY 

    OK: Go to next step 

  4. CHECK HARNESS AND CONNECTOR (STOP LIGHT CONTROL RELAY - BATTERY AND BODY GROUND) 
    1. Disconnect the A39 stop light control relay connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage 

      STANDARD VOLTAGE SPECIFICATION

      Tester Connection Condition Specified Condition
      A39-6 (+B) - Body ground Always 11 to 14 V
      Fig 2: Identifying A39 Stop Light Control Relay Connector
      G05760391Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance 

      STANDARD RESISTANCE SPECIFICATION

      Tester Connection Condition Specified Condition
      A39-4 (GND) - Body ground Always Below 1 Ω

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  5. CHECK HARNESS AND CONNECTOR (STOP LIGHT CONTROL RELAY - STOP LIGHT SWITCH) 
    1. Disconnect the A39 stop light control relay connector.
    2. Disconnect the A30 stop light switch connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance 

      STANDARD RESISTANCE SPECIFICATION

      Tester Connection Condition Specified Condition
      A30-1 - A39-2 (STP) Always Below 1 Ω
      A30-1 - Body ground Always 10 kΩ higher

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Fig 3: Identifying A39 Stop Light Control Relay And A30 Stop Light Switch Connectors
    G05760392Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: Go to next step 

  6. CHECK HARNESS AND CONNECTOR (STOP LIGHT CONTROL RELAY - BRAKE LIGHT RELAY) 
    1. Disconnect the A39 stop light control relay connector.
    2. Remove the brake light relay from the engine room relay block.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance 

      STANDARD RESISTANCE SPECIFICATION

      Tester Connection Condition Specified Condition
      A39-8 (OUT) - Brake light relay terminal 4 Always Below 1 Ω
      A39-8 (OUT) - Body ground Always 10 kΩ higher

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Fig 4: Identifying A39 Stop Light Control Relay Connector And Brake Light Relay
    G05760393Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: Go to next step 

  7. CHECK STOP LIGHT CONTROL RELAY 
    1. Remove the stop light control relay with its connector still connected (See RELAY ).
    2. Measure the voltage according to the value(s) in the table below.
      Fig 5: Identifying A39 Stop Light Control Relay Connector
      G05760394Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Voltage 

      STANDARD VOLTAGE SPECIFICATION

      Tester Connection Switch Condition Specified Condition
      A39-6 (+B) - A39-4 (GND) Always 11 to 14 V
      A39-2 (STP) - Body ground Stop light switch on (Brake pedal depressed) 11 to 14 V
      Stop light switch off (Brake pedal released) Below 1 V
      A39-8 (OUT) - Body ground Stop light switch on (Brake pedal depressed) 11 to 14 V
      Stop light switch off (Brake pedal released) Below 1 V

    NG: REPLACE STOP LIGHT CONTROL RELAY  (See RELAY )

    OK: Go to next step 

  8. CHECK HARNESS AND CONNECTOR (BRAKE LIGHT RELAY - BATTERY) 
    1. Remove the brake light relay from the engine room relay block.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage 

      STANDARD VOLTAGE SPECIFICATION

      Tester Connection Switch Condition Specified Condition
      Brake light relay terminal 1 - Body ground Engine switch on (IG) 11 to 14 V
      Brake light relay terminal 5 - Body ground

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Fig 6: Identifying Brake Light Relay
    G05760395Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: Go to next step 

  9. CHECK HARNESS AND CONNECTOR (BRK LP, STOP LIGHT CONTROL RELAY - MASTER CYLINDER SOLENOID) 
    1. Disconnect the A24 master cylinder solenoid (skid control ECU) connector.
      Fig 7: Identifying A24 Skid Control ECU And A39 Stop Light Control Relay Connectors
      G05760396Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Remove the brake light relay from the engine room relay block.
    3. Disconnect the A39 stop light control relay connector.
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance 

      STANDARD RESISTANCE SPECIFICATION

      Tester Connection Condition Specified Condition
      Brake light relay terminal 2 - A24-16 (STPO) Always Below 1 Ω
      A39-2 (STP) - A24-45 (STP2)
      Brake light relay terminal 3 - A24-7 (STP)
      Brake light relay terminal 2 - Body ground Always 10 kΩ higher
      A39-2 (STP) - Body ground
      Brake light relay terminal 3 - Body ground

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: REPLACE MASTER CYLINDER SOLENOID (SKID CONTROL ECU)  (See REMOVAL )

  10. INSPECT STOP LIGHT SWITCH 
    1. Disconnect the A30 stop light switch connector.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance 

      STANDARD RESISTANCE SPECIFICATION

      Tester Connection Switch Condition Specified Condition
      1-2 Pin not pushed Below 1 Ω
      Pin pushed 10 kΩ higher
      3-4 Pin not pushed 10 kΩ higher
      Pin pushed Below 1 Ω

    NG: REPLACE STOP LIGHT SWITCH  (See REMOVAL )

    Fig 8: Inspecting Stop Light Switch
    G05638364Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: Go to next step 

  11. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH - BATTERY) 
    1. Disconnect the A30 stop light switch connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage 

      STANDARD VOLTAGE SPECIFICATION

      Tester Connection Switch Condition Specified Condition
      A30-2 - Body ground Engine switch on (IG) 11 to 14 V
      A30-3 - Body ground

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Fig 9: Identifying A30 Stop Light Switch Connector
    G05638365Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: Go to next step 

  12. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH - ECM) 
    1. Disconnect the A38 ECM connector.
    2. Disconnect the A30 stop light switch connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance 

      STANDARD RESISTANCE SPECIFICATION

      Tester Connection Condition Specified Condition
      A30-4 - A38-35 (ST1-) Always Below 1 Ω
      A30-1 - A38-36 (STP)
      A30-1 - Body ground Always 10 kΩ higher
      A30-4 - Body ground

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Fig 10: Identifying A30 Stop Light Switch And A38 ECM Connectors
    G05638366Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: REPLACE ECM  (See ECM )

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