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Home >> Lexus >> 2023 >> RC F Base >> Repair and Diagnosis (Single Page) >> Restraints >> Restraints Control Systems >> Pre-Collision System - Diagnostic Codes (1 Of 2) >> Pre-Collision System >> DTC C1A4B: Stop Light Relay Circuit [09/2014 - 11/2017] >> Procedure

DTC C1A4B: Stop Light Relay Circuit [09/2014 - 11/2017]: 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

      Proceed to
      OK
      NG

    Result: 

    NG 

    GO TO LIGHTING SYSTEM 

    for Single Beam Headlight: Refer to HOW TO PROCEED WITH TROUBLESHOOTING [09/2014 - 03/2019]

    for Triple Beam Headlight: Refer to HOW TO PROCEED WITH TROUBLESHOOTING [09/2014 - 03/2019]

    Result: 

    OK 

    See step  2

  2. CHECK TERMINAL VOLTAGE (POWER SOURCE OF SEMICONDUCTOR PWR INTEGRATION ECU) 
    1. Turn the engine switch off.
    2. Disconnect the 2B semiconductor PWR integration ECU connector.
      GTY465809Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Semiconductor PWR Integration ECU)
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      2B-1 (BATT) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (SEMICONDUCTOR PWR INTEGRATION ECU - BODY GROUND) 
    1. Turn the engine switch off.
    2. Disconnect the 2D and 2G semiconductor PWR integration ECU connectors.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      2D-14 - Body ground Always Below 1 Ω
      2G-5 - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. CHECK TERMINAL VOLTAGE (STP TERMINAL) 
    1. Turn the engine switch off.
    2. Disconnect the A15 brake actuator assembly (skid control ECU) connector.
      GTY459315Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Brake Actuator Assembly (Skid Control ECU))
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A15-2 (STP) - Body ground Brake pedal depressed 11 to 14 V
      A15-2 (STP) - Body ground Brake pedal released Below 1.5 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  5

  5. CHECK TERMINAL VOLTAGE (STP TERMINAL) 
    1. Turn the engine switch off.
    2. Disconnect the 2D semiconductor PWR integration ECU connector.
      GTY460021Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Semiconductor PWR Integration ECU)
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      2D-10 (STP) - Body ground Brake pedal depressed 11 to 14 V
      2D-10 (STP) - Body ground Brake pedal released Below 1.5 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  6

  6. PERFORM ACTIVE TEST USING TECHSTREAM (STOP LIGHT RELAY) 
    1. Enter the following menus: Chassis / ABS/VSC/TRAC / Active Test.
    2. Perform "Active Test" according to the display on the Techstream.

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display Measurement Item Control Range Diagnostic Note
      Stop Light Relay Stop light control relay (STOP LP) ON or OFF Stop lights come on

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display
      Stop Light Relay
    3. Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.
    4. Check the stop light switch assembly (stop light control relay) operation using the Data List and stop light operation by performing an Active Test.

      Chassis > ABS/VSC/TRAC > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Stop Light Relay Output Stop light control relay (STOP LP) output ON or OFF ON: Relay output on (Stop light on)
      OFF: Relay output off (Stop light off)      		 -

      Chassis > ABS/VSC/TRAC > Data List 

      Tester Display
      Stop Light Relay Output

      Result

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

    Result: 

    B 

    See step  8

    Result: 

    A 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (BRAKE ACTUATOR ASSEMBLY (SKID CONTROL ECU) - SEMICONDUCTOR PWR INTEGRATION ECU) 
    1. Turn the engine switch off.
    2. Disconnect the A15 brake actuator assembly (skid control ECU) connector.
    3. Disconnect the 2D semiconductor PWR integration ECU connector.
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A15-31 (STPO) - 2D-3 (ACC) Always Below 1 Ω
      A15-31 (STPO) or 2D-3 (ACC) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  8

  8. CHECK HARNESS AND CONNECTOR (BRAKE ACTUATOR ASSEMBLY (SKID CONTROL ECU) - SEMICONDUCTOR PWR INTEGRATION ECU) 
    1. Turn the engine switch off.
    2. Disconnect the A15 brake actuator assembly (skid control ECU) connector.
    3. Disconnect the 2F semiconductor PWR integration ECU connector.
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A15-22 (STP2) - 2F-9 (OUT) Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  9

  9. CHECK TERMINAL VOLTAGE (STP2 TERMINAL) 
    1. Turn the engine switch off.
    2. Disconnect the A15 brake actuator assembly (skid control ECU) connector.
      GTY459308Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Brake Actuator Assembly (Skid Control ECU))
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A15-22 (STP2) - Body ground Brake pedal depressed 11 to 14 V
      A15-22 (STP2) - Body ground Brake pedal released Below 1.5 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE SEMICONDUCTOR PWR INTEGRATION ECU. Refer to  REMOVAL [09/2014 - ] 

    Result: 

    OK 

    See step  10

  10. CHECK FOR DTCs (PRE-COLLISION 2) 
    1. Turn the engine switch off and wait for at least 2 minutes.
    2. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [09/2014 - 11/2017]

      Body Electrical > Pre-Collision 2 > Clear DTCs 

    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 - 11/2017]

      Body Electrical > Pre-Collision 2 > Trouble Codes 

      NOTE:

      When replacing the driving support ECU assembly, always replace it with a new one. If a driving support ECU assembly which was installed to another vehicle is used, the information stored in the driving support ECU assembly will not match the information from the vehicle. As a result, a DTC may be stored.

      Result

      Result Proceed to
      DTC C1A4B is not output A
      DTC C1A4B is output B

    Result: 

    A 

    END 

    Result: 

    B 

    REPLACE DRIVING SUPPORT ECU ASSEMBLY. Refer to  REMOVAL [09/2014 - 01/2023] 

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