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

A01XGPBE21
*1 Engine Switch
*2 Certification ECU

CAUTION / NOTICE / HINT

Note

Before replacing the certification ECU, refer to the Service Bulletin.

PROCEDURE


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


    1. Disconnect the G38 ECU connector.

    2. Disconnect the G36 switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      G38-28 (VC5) - G36-14 (VC5) Always Below 1 Ω
      G38-36 (AGND) - G36-8 (AGND)
      G38-28 (VC5) or G36-14 (VC5) - Body ground Always 10 kΩ or higher
      G38-36 (AGND) or G36-8 (AGND) - Body ground

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  2. CHECK CERTIFICATION ECU


    1. Using an oscilloscope, check the waveform.

      A01XEHAE01
      Measurement Condition
      Item Content
      Tester Connection G36-14 (VC5) - G36-8 (AGND)
      Tool Setting 2 V/DIV., 20 ms./DIV.
      Condition Engine switch off, key not in cabin, and 30 seconds or less after engine switch pushed
      OK
      Waveform is output normally (refer to illustration).
      Text in Illustration
      *a

      Component with harness connected

      (Engine Switch)

      Tech Tips

      If replacing the Engine Switch, refer to the procedures below.



    OK

    REPLACE ENGINE SWITCH

    NG

    REPLACE CERTIFICATION ECU