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 No. DTC Detection Condition Trouble Area
B278A Engine switch power source supply line is open or shorted.

  • Wire harness or connector

  • Engine switch

  • Certification ECU

WIRING DIAGRAM

A011BY6E18

INSPECTION PROCEDURE

Note

If the certification ECU is replaced, register the key.

PROCEDURE


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

    A011B06E01
    Text in Illustration
    *1

    Front view of wire harness connector

    (to Certification ECU)

    		 *2

    Front view of wire harness connector

    (to Engine Switch)

    1. Disconnect the certification ECU connector.

    2. Disconnect the engine switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      D34-28 (VC5) -D27-14 (VC5) Always Below 1 Ω
      D34-36 (AGND) - D27-8 (AGND) Always Below 1 Ω
      D34-28 (VC5) - Body ground Always 10 kΩ or higher
      D34-36 (AGND) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  2. CHECK HARNESS AND CONNECTOR (ENGINE SWITCH - POWER SOURCE AND BODY GROUND)


    1. Reconnect the certification ECU connector.

    2. A011B4PE01
      Text in Illustration
      *1

      Component with harness connected

      (Engine Switch)

      Reconnect the engine switch connector.

    3. Using an oscilloscope, check the waveform.

      Waveform
      Item Content
      Tester Connection D27-14(VC5) - D27-8(AGND)
      Tool Setting 2 V/DIV - 200 ms./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)

    NG

    REPLACE CERTIFICATION ECU

    OK

    REPLACE ENGINE SWITCH Click here