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DTC C1A4B: Stop Light Relay Circuit [08/2015 - ]: 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 ALL Stop Light do not Illuminate [08/2015 - ] )

    Result: 

    OK 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (MASTER CYLINDER SOLENOID STPO TERMINAL VOLTAGE) 
    1. Disconnect the master cylinder solenoid (skid control ECU) connector.
    2. Measure the voltage according to the value(s) in the table below.
      GTY539266Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Voltage

      Tester Connection Condition Specified Condition
      A24-16 (STPO) - Body ground Engine switch on (IG) 11 to 14 V
      TEXT IN ILLUSTRATION

      *a Front view of wire harness connector
      (to Master Cylinder Solenoid [Skid Control ECU])

    Result: 

    NG 

    See step  7

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (MASTER CYLINDER SOLENOID STP2 TERMINAL VOLTAGE) 
    1. Disconnect the master cylinder solenoid (skid control ECU) connector.
    2. Measure the voltage according to the value(s) in the table below.
      GTY561908Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Voltage

      Tester Connection Condition Specified Condition
      A24-45 (STP2) - Body ground Brake pedal depressed 11 to 14 V
      TEXT IN ILLUSTRATION

      *a Front view of wire harness connector
      (to Master Cylinder Solenoid [Skid Control ECU])

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

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

      Tester Display Test Part Control Range Diagnostic Note
      Stop Light Relay Brake light relay (STP LP OPE) Relay ON/OFF Observe the stop light (the stop lights do not come on for 2 to 5 seconds).
    3. Check the brake light relay (STP LP OPE) operation using the Data List and stop light operation by performing an Active Test.
      ABS/VSC/TRAC

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

      Result

      Result Proceed to
      The Data List item "Stop Light Relay Output" switches between ON and OFF when turning the stop light control relay on and off with the Active Test, but the stop lights do not illuminate or turn off A
      The Data List item "Stop Light Relay Output" does not switch between ON and OFF when turning the stop light control relay on and off with the Active Test B
      The Data List item "Stop Light Relay Output" switches between ON and OFF when turning the stop light control relay on and off with the Active Test and the stop lights illuminate and turn off

    Result: 

    B 

    REPLACE MASTER CYLINDER SOLENOID (SKID CONTROL ECU) 

    (Refer to DISASSEMBLY [08/2015 - ] )

    Result: 

    A 

    See step  5

  5. INSPECT BRAKE LIGHT RELAY (STP LP OPE) 
    1. Turn the engine switch off.
    2. Remove the brake light relay (STP LP OPE) from the engine room relay block and junction block assembly.
    3. Inspect the brake light relay (STP LP OPE) (Refer to ON-VEHICLE INSPECTION [08/2015 - ] ).

    Result: 

    NG 

    REPLACE BRAKE LIGHT RELAY (STP LP OPE) 

    Result: 

    OK 

    See step  6

  6. CHECK HARNESS AND CONNECTOR (BRAKE LIGHT RELAY - BATTERY) 
    1. Turn the engine switch off.
    2. Remove the brake light relay (STP LP OPE) from the engine room relay block and junction block assembly.
    3. Measure the voltage according to the value(s) in the table below.
      GTY595306Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Voltage

      Tester Connection Condition Specified Condition
      Brake light relay (STP LP OPE) holder terminal 5 - Body ground Always 11 to 14 V
      TEXT IN ILLUSTRATION

      *1 Engine Room Relay Block and Junction Block Assembly
      *2 Brake Light Relay (STP LP OPE) Holder Terminal

    Result: 

    OK 

    REPLACE MASTER CYLINDER SOLENOID (SKID CONTROL ECU) 

    (Refer to DISASSEMBLY [08/2015 - ] )

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  7. CHECK HARNESS AND CONNECTOR (BRAKE LIGHT RELAY - MASTER CYLINDER SOLENOID AND BATTERY) 
    1. Turn the engine switch off.
    2. Remove the brake light relay (STP LP OPE) from the engine room relay block and junction block assembly.
    3. Disconnect the A24 master cylinder solenoid (skid control ECU) connector.
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      Brake light relay (STP LP OPE) holder terminal 2 - A24-16 (STPO) Always Below 1 Ω
      STP LP OPE relay (brake light relay) holder terminal 2 or A24-16 (STPO) - Body ground Always 10 kΩ or higher
    5. Measure the voltage according to the value(s) in the table below.
      GTY595306Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      brake light relay (STP LP OPE) holder terminal 1 - Body ground Engine switch on (IG) 11 to 14 V
      TEXT IN ILLUSTRATION

      *1 Engine Room Relay Block and Junction Block Assembly
      *2 Brake Light Relay (STP LP OPE) Holder Terminal

    Result: 

    OK 

    REPLACE BRAKE LIGHT RELAY (STP LP OPE) 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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