ENGINE IMMOBILISER 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 power switch power source supply line is open or shorted.

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

  • Wire harness or connector

  • Power switch

  • Certification ECU (Smart key ECU assembly)

WIRING DIAGRAM

A004077E31

INSPECTION PROCEDURE

Note

If the certification ECU (smart key ECU assembly) is replaced, register all the keys.

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 - POWER SWITCH) Click here

    OK

    USE SIMULATION METHOD TO CHECK Click here

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


    1. Disconnect the L56 certification ECU (smart key ECU assembly) connector.

    2. Disconnect the L33 power switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      L56-28 (VC5) - L33-14 (VC5) Always Below 1 Ω
      L56-36 (AGND) - L33-8 (AGND) Always Below 1 Ω
      L56-28 (VC5) - Body ground Always 10 kΩ or higher
      L56-36 (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 L56 certification ECU (smart key ECU assembly) connector.

    2. Reconnect the L33 power switch connector.

    3. A0042I4E08
      Text in Illustration
      *1 GND
      *a

      Component with harness connected

      (Power Switch)

      Using an oscilloscope, check the waveform.

      Waveform (Reference)
      Item Content
      Tester Connection L33-14 (VC5) - L33-8 (AGND)
      Tool Setting 2 V/DIV., 200 ms./DIV.
      Condition

      • Power switch off

      • Key not in cabin

      • Within 30 seconds after power switch pressed
      OK
      Waveform is output normally (see illustration)

    NG

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

    OK

    REPLACE POWER SWITCH Click here