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

A01IUBUE18

INSPECTION PROCEDURE

PROCEDURE


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


    1. Disconnect the H51 ECU connector.

      A01IPNZE02
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Certification ECU)

      		 *2

      Front view of wire harness connector

      (to Engine Switch)

    2. Disconnect the H53 switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      H51-28 (VC5) - H53-14 (VC5) Always Below 1 Ω
      H51-36 (AGND) - H53-8 (AGND)
      H51-28 (VC5) or H53-14 (VC5) - Body ground Always 10 kΩ or higher
      H51-36 (AGND) or H53-8 (AGND) - Body ground

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  2. CHECK CERTIFICATION ECU


    1. A01IO4ME01

      Using an oscilloscope, check the waveform.

      Measurement Condition
      Item Content
      Tester Connection H53-14 (VC5) - H53-8 (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).

      Tech Tips

      If replacing the engine switch, refer to the procedures below.



    NG

    REPLACE CERTIFICATION ECU

    OK

    REPLACE ENGINE SWITCH