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Home >> Lexus >> 2021 >> UX 250h Base >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Anti-Theft Systems >> Smart Access System W/ Push-Button Start (Start Function) (Diagnostic Codes & Symptom Tests (1 Of 2)) (Hybrid) >> SMART ACCESS SYSTEM WITH PUSH-BUTTON START (for Start Function, HV Model) >> DTC B2284: Brake Signal Malfunction [10/2018 - ] >> Procedure

DTC B2284: Brake Signal Malfunction [10/2018 - ]: Procedure

  1. READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH1) 
    1. Connect the Techstream to the DLC3.
    2. Turn the power switch on (IG).
    3. Turn the Techstream on.
    4. Enter the following menus: Body Electrical / Power Source Control / Data List.
    5. Read the Data List according to the display on the Techstream.

      Body Electrical > Power Source Control > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Stop Light Switch1 State of brake pedal OFF or ON OFF: Brake pedal released
      ON: Brake pedal depressed
      • Use this item to determine if the stop light switch assembly is malfunctioning.
      • The hybrid control system cannot be started when this item is OFF.
      • If the stop light switch assembly is malfunctioning, the hybrid control system can be started by pressing and holding the power switch for a certain period of time.

      Body Electrical > Power Source Control > Data List 

      Tester Display
      Stop Light Switch1

      OK

      The Techstream display changes correctly in response to the brake pedal operation.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    GO TO ELECTRONICALLY CONTROLLED BRAKE SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING). Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [10/2018 - ] 

    Result: 

    NG 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - STOP LIGHT SWITCH ASSEMBLY) 
    1. Disconnect the N61 certification ECU (smart key ECU assembly) connector.
    2. Disconnect the A42 stop light switch assembly connector.
    3. Disconnect the A37 skid control ECU (brake booster with master cylinder assembly) connector.
    4. Disconnect the A46 hybrid vehicle control ECU connector.
    5. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      N61-25 (STP1) - A42-3 (L) Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  3

  3. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) 
    1. Connect the N61 certification ECU (smart key ECU assembly) connector.
    2. Connect the A42 stop light switch assembly connector.
    3. Measure the voltage according to the value(s) in the table below.
      GTY787258Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Certification ECU (Smart Key ECU Assembly))

      Standard Voltage

      Tester Connection Condition Specified Condition
      N61-25 (STP1) - Body ground Brake pedal released → depressed 1 V or less → 9 V or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY). Refer to  REMOVAL [10/2018 - 07/2022]  Refer to  REMOVAL [07/2022 - ] 

    Result: 

    NG 

    REPLACE STOP LAMP SWITCH ASSEMBLY. Refer to  REMOVAL [10/2018 - ] 

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