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Home >> Lexus >> 2020 >> GS 350 Base, RWD >> Repair and Diagnosis >> Restraints >> Restraints Control Systems >> Pre-Collision System - Diagnostic Codes & Circuit Tests >> Pre-Collision System >> DTC C1A4B: Stop Light Relay Circuit [09/2014 - 10/2015] >> Procedure
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DTC C1A4B: Stop Light Relay Circuit [09/2014 - 10/2015]: Procedure

  1. CHECK STOP LIGHT OPERATION 
    1. Check that the stop lights come on when the brake pedal is depressed, and go off when the brake pedal is released.

      OK

      Condition Illumination Condition
      Brake pedal depressed ON
      Brake pedal released OFF

    Result: 

    NG 

    GO TO LIGHTING SYSTEM 

    (Refer to HOW TO PROCEED WITH TROUBLESHOOTING [09/2014 - 10/2015] )

    Result: 

    OK 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (NO. 2 INTEGRATION RELAY POWER SOURCE TERMINAL) 
    1. Turn the engine switch off.
      GTY666800Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the No. 2 integration relay connectors.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      2B-7 (BATT) - Body ground Always 11 to 14 V
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      2A-22 (GNDA) - Body ground Always Below 1 Ω
      2B-10 (GNDB) - Body ground Always Below 1 Ω
      TEXT IN ILLUSTRATION

      *a Front view of wire harness connector
      (to No. 2 Integration Relay)

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (STP TERMINAL) 
    1. Turn the engine switch off.
    2. Make sure that there is no looseness at the locking part and the connecting part of the connector.
      GTY677583Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    3. Disconnect the brake actuator assembly connector.
    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A13-2 (STP) - Body ground Brake pedal depressed 11 to 14 V
      Brake pedal released Below 1.5 V
      TEXT IN ILLUSTRATION

      *a Front view of wire harness connector
      (to Brake Actuator Assembly)

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (BATTERY - NO. 2 INTEGRATION RELAY) 
    1. Turn the engine switch off.
    2. Disconnect the No. 2 integration relay connector.
      GTY668246Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      2A-11 (STPO) - Body ground Brake pedal depressed 11 to 14 V
      Brake pedal released Below 1.5 V
      TEXT IN ILLUSTRATION

      *a Front view of wire harness connector
      (to No. 2 Integration Relay)

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  5

  5. PERFORM ACTIVE TEST USING TECHSTREAM (STOP LIGHT RELAY) 
    1. Turn the engine switch off.
    2. Connect the Techstream to the DLC3.
    3. Start the engine.
    4. Turn the Techstream on.
    5. Enter the following menus: Chassis / ABS/VSC/TRAC / Active Test.
      ABS/VSC/TRAC

      Tester Display Test Part Control Range Diagnostic Note
      Stop Light Relay No. 2 integration relay ON / OFF Observe the stop light (the stop lights do not come on for 2 to 5 seconds).
    6. While performing the Active Test, check the illumination condition of the stop lights and "Stop Light Relay Output" in the Data List.
      ABS/VSC/TRAC

      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Stop Light Relay Output No. 2 integration relay output / ON or OFF ON: Relay output ON
      OFF: Relay output OFF      		 -
      RESULT

      Result Proceed to
      When Active Test performed, Data List item changes between ON and OFF, but stop lights do not turn on A
      When Active Test performed, Data List item changes between ON and OFF and stop lights turn on and off B

    Result: 

    B 

    See step  7

    Result: 

    A 

    See step  6

  6. CHECK HARNESS AND CONNECTOR (NO. 2 INTEGRATION RELAY - BRAKE ACTUATOR ASSEMBLY) 
    1. Turn the engine switch off.
    2. Disconnect the 2A No. 2 integration relay connector.
    3. Disconnect the A13 skid control ECU (brake actuator assembly) connector.
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      2A-7 (ACC) - A13-31 (STPO) Always Below 1 Ω
      2A-7 (ACC) - Body ground Always 10 kΩ or higher
      2A-18 (ESS) - A13-8 (EXO)* Always Below 1 Ω
      2A-18 (ESS) - Body ground* Always 10 kΩ or higher
      1. *: w/ Emergency Brake Signal

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (NO. 2 INTEGRATION RELAY - BRAKE ACTUATOR ASSEMBLY) 
    1. Turn the engine switch off.
    2. Disconnect the 2A No. 2 integration relay connector.
    3. Disconnect the A13 skid control ECU (brake actuator assembly) connector.
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      2A-3 (STOP) - A13-22 (STP2) Always Below 1 Ω
      2A-3 (STOP) - Body ground Always 10 kΩ or higher

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  8

  8. CHECK HARNESS AND CONNECTOR (STP2 TERMINAL) 
    1. Turn the engine switch off.
    2. Make sure that there is no looseness at the locking part and the connecting part of the connector.
    3. Disconnect the brake actuator assembly connector.
      GTY676210Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A13-22 (STP2) - Body ground Brake pedal depressed 11 to 14 V
      Brake pedal released Below 1.5 V
      TEXT IN ILLUSTRATION

      *a Front view of wire harness connector
      (to Brake Actuator Assembly)

    Result: 

    NG 

    REPLACE NO. 2 INTEGRATION RELAY 

    (Refer to REMOVAL [09/2014 - ] )

    Result: 

    OK 

    See step  9

  9. CHECK FOR DTC 
    1. Turn the engine switch off and wait for at least 2 minutes.
    2. Clear the DTCs (Refer to DTC CHECK / CLEAR [09/2014 - 10/2015] ).
    3. Make sure that the DTC detection conditions are met.

      HINT: 

      If the detection conditions are not met, the system cannot detect the malfunction.

      • Using the Techstream, perform the Active Test "Stop Light Relay" with the engine switch on (IG).
    4. Check for DTCs (Refer to DTC CHECK / CLEAR [09/2014 - 10/2015] ).
      NOTE:

      When replacing the driving support ECU, always replace it with a new one and be sure to perform initialization (Refer to INITIALIZATION [09/2014 - 10/2015] ). If an ECU which was installed to another vehicle is used, the information stored in the ECU will not match the information from the vehicle, and as a result, a DTC may be stored.

      OK

      DTC C1A4B is not output.

    Result: 

    OK 

    END 

    Result: 

    NG 

    REPLACE DRIVING SUPPORT ECU 

    (Refer to REMOVAL [09/2014 - 10/2015] )

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