ENGINE IMMOBILISER SYSTEM, Diagnostic DTC:B278A

DTC Code DTC Name
B278A Short to GND in Immobiliser System Power Source Circuit

DESCRIPTION

When there is a short to GND in the power supply for the transponder key amplifier of the power switch, the certification ECU (smart key ECU assembly) stores this DTC.

DTC Code DTC Detection Condition Trouble Area DTC Output Confirmation Operation
B278A A short to GND in the power supply of the transponder key amplifier of the power switch (VC5 - VC5) (1 trip detection logic*).

  • Wire harness or connector


  • Power switch


  • Certification ECU (smart key ECU assembly)

 With park (P) selected, the key is held against the power switch and a hybrid control system start operation is performed by pressing and holding the power switch when the key battery is depleted.

Vehicle Condition and Fail-safe Operation when Malfunction Detected
Vehicle Condition when Malfunction Detected Fail-safe Operation when Malfunction Detected
Hybrid control system cannot be started when key battery is depleted by holding key against power switch and pressing and holding power switch with park (P) selected -
Related Data List and Active Test
DTC Code Data List and Active Test
B278A -

WIRING DIAGRAM

A003ZCCE45

INSPECTION PROCEDURE

Note


  • Before replacing the certification ECU (smart key ECU assembly), refer to the Service Bulletin.

  • The fixed 5 V power source voltage in the power switch is output through a resistance from terminal VC5.

  • Terminal AGND is grounded through both the power switch and certification ECU (smart key ECU assembly).

  • After performing repair, perform the operation that fulfills the DTC output confirmation operation, and then confirm that no DTCs are output again.

PROCEDURE


  1. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - POWER SWITCH)


    1. Disconnect the H1*1 or H143*2 ECU connector.


      • *1: w/ Entry Function

      • *2: w/o Entry Function

    2. Disconnect the H78 switch connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition

      H1-28 (VC5) - H78-14 (VC5)*1

      H143-28 (VC5) - H78-14 (VC5)*2

      		 Always Below 1 Ω

      H1-36 (AGND) - H78-8 (AGND)*1

      H143-36 (AGND) - H78-8 (AGND)*2

      H1-28 (VC5) or H78-14 (VC5) - Body ground*1

      H143-28 (VC5) or H78-14 (VC5) - Body ground*2

      		 Always 10 kΩ or higher

      H1-36 (AGND) or H78-8 (AGND) - Body ground*1

      H143-36 (AGND) or H78-8 (AGND) - Body ground*2

      • *1: w/ Entry Function

      • *2: w/o Entry Function


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  2. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. A003X6DE13
      Text in Illustration
      *a

      Component with harness connected

      (Power Switch)

      Using an oscilloscope, check the waveform.

      Tech Tips

      Perform this inspection on the power switch side.

      Measurement Condition
      Item Content
      Tester Connection H78-14 (VC5) - H78-8 (AGND)
      Tool Setting 2 V/DIV., 200 ms./DIV.
      Condition After power switch turned off, within 30 seconds of any door opened and closed, or brake pedal depressed
      OK
      Waveform is output normally (refer to illustration).
      Result
      Result Proceed to
      OK (for 2ZR-FXE) A
      OK (for 5ZR-FXE) B
      NG C

    B

    REPLACE POWER SWITCH Click here

    C

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

    A

    REPLACE POWER SWITCH Click here