ENGINE IMMOBILISER SYSTEM (w/ Smart 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 (Smart key ECU assembly)

WIRING DIAGRAM

A01EL7WE19

INSPECTION PROCEDURE

Note

If the certification ECU (smart key ECU assembly) is replaced, register the key (Refer to Service Bulletin).

PROCEDURE


  1. CHECK DTC OUTPUT


    1. Clear the DTCs Click here.

    2. Recheck for DTCs Click here.

      OK
      DTC B278A is not output.

    NG

    CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - ENGINE SWITCH) Click here

    OK

    USE SIMULATION METHOD TO CHECK Click here

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


    1. Disconnect the certification ECU (smart key ECU assembly) connector.

    2. A01EM23E01
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Certification ECU (Smart Key ECU Assembly))
      *2

      Front view of wire harness connector

      (to Engine Switch)

      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
      D25-28 (VC5) - D13-14 (VC5) Always Below 1 Ω
      D25-36 (AGND) - D13-8 (AGND) Always Below 1 Ω
      D25-28 (VC5) - Body ground Always 10 kΩ or higher
      D25-36 (AGND) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. Reconnect the certification ECU (smart key ECU assembly) connector.

    2. Reconnect the engine switch connector.

    3. Using an oscilloscope, check the waveform.

      A01EMJXE01
      Waveform (Reference)
      Item Content
      Tester Connection D25-28 (VC5) - D25-36 (AGND)
      Tool Setting 2 V/DIV., 200 ms./DIV.
      Condition

      • Engine switch off

      • Key not in cabin

      • Engine switch pressed within 30 seconds
      Text in Illustration
      *1

      Component with harness connected

      (Certification ECU (Smart Key ECU Assembly))
      *2 GND
      OK
      Waveform is output normally (see illustration)

    NG

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

    OK

    REPLACE ENGINE SWITCH Click here