ENGINE IMMOBILISER SYSTEM (w/ Smart Key System), Diagnostic DTC:B278A

DTC Code DTC Name
B278A Short to GND in Immobiliser System Power Source Circuit

DESCRIPTION

When there is a short to GND in the power supply for the transponder key amplifier of the engine switch, the certification ECU (smart key ECU assembly) stores this DTC.

DTC Code DTC Detection Condition Trouble Area DTC Output Confirmation Operation
B278A A short to GND in the power supply of the transponder key amplifier of the engine switch (VC5 - VC5) (1 trip detection logic*).

  • Wire harness or connector


  • Engine switch


  • Certification ECU (smart key ECU assembly)

 With the shift lever in P, the key held near the engine switch and an engine start operation is performed by pressing and holding the engine switch when the key battery is depleted.

Vehicle Condition and Fail-safe Operation when Malfunction Detected
Vehicle Condition when Malfunction Detected Fail-safe Operation when Malfunction Detected
Engine cannot be started when key battery is depleted by holding key near engine switch and pressing and holding engine switch with shift lever in P -
Related Data List and Active Test
DTC Code Data List and Active Test
B278A -

WIRING DIAGRAM

A01I0L3E08

INSPECTION PROCEDURE

Note


  • Before replacing the certification ECU (smart key ECU assembly), refer to Registration Click here.

  • After performing repairs, perform the operation that fulfills the DTC output confirmation operation, and then confirm that no DTCs are output again.

PROCEDURE


  1. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. Using an oscilloscope, check the waveform.

      A01HYL1E01
      Text in Illustration
      *a

      Component with harness connected

      (Engine Switch)

      		 *b Waveform

      Tech Tips

      Perform this inspection on the engine switch side.

      Measurement Condition
      Tester Connection Condition Tool Setting Specified Condition
      I58-10 (VC5) - I58-6 (AGND) Engine switch off, key not in cabin, within 30 seconds after engine switch pressed 2 V/DIV., 200 ms./DIV.

      Pulse generation

      (See waveform)
      OK
      The waveform is similar to that shown in the illustration.
      Result
      Result Proceed to
      NG A
      OK (for 2GR-FE) B
      OK (for 2AR-FE) C

    B

    REPLACE ENGINE SWITCH Click here

    C

    REPLACE ENGINE SWITCH Click here

    A

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


    1. Disconnect the I78 certification ECU (smart key ECU assembly) connector.

    2. Disconnect the I58 engine switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      I78-1 (VC5) - I58-10 (VC5) Always Below 1 Ω
      I78-24 (AGND) - I58-6 (AGND) Always Below 1 Ω
      I78-1 (VC5) or I58-10 (VC5) - Body ground Always 10 kΩ or higher
      I78-24 (AGND) or I58-6 (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 I78 certification ECU (smart key ECU assembly) connector.

    2. Reconnect the I58 engine switch connector.

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

      A01I1NZE36
      Text in Illustration
      *a

      Component with harness connected

      (Certification ECU (Smart Key ECU Assembly))

      		 - -
      Standard Voltage
      Tester Connection Condition Specified Condition
      I78-1 (VC5) - I78-24 (AGND) Engine switch off, brake pedal not depressed, 30 seconds or more elapsed after driver door opened and then closed Below 1 V
      Result
      Result Proceed to
      OK (for 2GR-FE) A
      OK (for 2AR-FE) B
      NG C

    B

    REPLACE ENGINE SWITCH Click here

    C

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) Click here

    A

    REPLACE ENGINE SWITCH Click here