ENGINE IMMOBILISER SYSTEM(w/ Entry and Start System), Diagnostic DTC:B278A

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

DESCRIPTION

This DTC is stored when the engine switch power source supply line is open or shorted.

DTC Code DTC Detection Condition Trouble Area
B278A The engine switch power source supply line is open or shorted.

  • Harness or connector


  • Engine switch


  • Certification ECU

WIRING DIAGRAM

A004RW2E62
*1 Engine Switch
*2 Certification ECU

PROCEDURE


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

    A004U1OE02

    1. Disconnect the D54 ECU connector.

    2. Disconnect the D56 switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      D54-28 (VC5) - D56-14 (VC5) Always Below 1 Ω
      D54-36 (AGND) - D56-8 (AGND)
      D54-28 (VC5) or D56-14 (VC5) - Body ground Always 10 kΩ or higher
      D54-36 (AGND) or D56-8 (AGND) - Body ground
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Certification ECU)

      		 *2

      Front view of wire harness connector

      (to Engine Switch)

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  2. INSPECT CERTIFICATION ECU

    A004RJ7E01
    *1 Front view of wire harness connector: (to Engine Switch)

    1. Disconnect the D56 switch connector.

    2. Using an oscilloscope, check the waveform.

      Waveform (Reference)
      Item Content
      Tester Connection D56-14 (VC5) - D56-8 (AGND)
      Tool Setting 2 V/DIV - 200 s./DIV
      Condition Engine switch off, key not in cabin, and 30 seconds or less after engine switch pushed.
      OK
      Waveform is output normally (See illustration).
      Result
      Result Proceed to
      OK (for 1WW) A
      OK (for 2WW) B
      NG C

    A

    REPLACE ENGINE SWITCH Click here

    B

    REPLACE ENGINE SWITCH Click here

    C

    REPLACE CERTIFICATION ECU