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Home >> Toyota >> 2021 >> Highlander LE, 4WD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 4 (Smart Key System (For Start, HV) - Diagnostic Codes (1 Of 2)) >> SMART KEY SYSTEM (for Start Function, HV Model) >> DTC B278A: Short to GND in Immobiliser System Power Source Circuit [12/2019 - 11/2023] >> Procedure

DTC B278A: Short to GND in Immobiliser System Power Source Circuit [12/2019 - 11/2023]: Procedure

WARNING: This page is about a different variant/trim than selected.
  1. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) 
    1. Using an oscilloscope, check the waveform.
      GTY855893Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Power switch)      		 - -

      HINT: 

      Perform this inspection on the power switch side.

      Measurement Condition

      Tester Connection Condition Tool Setting Specified Condition
      H50-10 (VC5) - H50-6 (AGND) Ignition switch off, electrical key transmitter sub-assembly not in cabin, within 30 seconds of power switch pressed 2 V/DIV., 200 ms./DIV. Pulse generation

      OK

      The waveform is similar to that shown in the illustration.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE POWER SWITCH. Refer to  REMOVAL [12/2019 - 10/2022]  , or refer to  REMOVAL [10/2022 - 11/2023] 

    Result: 

    NG 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - POWER SWITCH) 
    1. Disconnect the H48 certification ECU (smart key ECU assembly) connector.
    2. Disconnect the H50 power switch connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      H48-7 (VC5) - H50-10 (VC5) Always Below 1 Ω
      H48-11 (AGND) - H50-6 (AGND) Always Below 1 Ω
      H48-7 (VC5) or H50-10 (VC5) - Other terminals and body ground Always 10 kΩ or higher
      H48-11 (AGND) or H50-6 (AGND) - Other terminals and body ground Always 10 kΩ or higher

      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 H48 certification ECU (smart key ECU assembly) connector.
    2. Connect the H50 power switch connector.
    3. Measure the voltage according to the value(s) in the table below.
      GTY873302Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Certification ECU (Smart Key ECU Assembly))

      Standard Voltage

      Tester Connection Condition Specified Condition
      H48-7 (VC5) - H48-11 (AGND) Ignition switch off, brake pedal not depressed, 30 seconds or more after driver door opened and then closed Below 1 V

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE POWER SWITCH. Refer to  REMOVAL [12/2019 - 10/2022]  , or refer to  REMOVAL [10/2022 - 11/2023] 

    Result: 

    NG 

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY). Refer to  REMOVAL [12/2019 - 11/2023] 

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