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

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 No. Detection Item DTC Detection Condition Trouble Area Note
B278A Short to GND in Immobiliser System Power Source Circuit A short to GND in the power supply of the transponder key amplifier of the engine switch (VC5 - VC5) (1 trip detection logic*).

  • Harness or connector

  • Engine switch

  • Certification ECU (smart key ECU assembly)

DTC Output Confirmation Operation:

With the shift lever in P (except Manual Transaxle), the key is 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.

*: Only output while a malfunction is present.

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 (except Manual Transaxle) -
Related Data List and Active Test
DTC No. Data List and Active Test
B278A -

WIRING DIAGRAM

A01QQQ3E19
*a Engine Switch
*b Certification ECU (Smart Key ECU Assembly)

CAUTION / NOTICE / HINT

Note


  • Before replacing the certification ECU (smart key ECU assembly), refer to the Service Bulletin.

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

PROCEDURE


  1. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU [SMART KEY ECU ASSEMBLY] - ENGINE SWITCH)


    1. Disconnect the G84 certification ECU (smart key ECU assembly) connector.

    2. Disconnect the G24 engine switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      G84-1 (VC5) - G24-10 (VC5) Always Below 1 Ω
      G84-24 (AGND) - G24-6 (AGND) Always Below 1 Ω
      G84-1 (VC5) - Body ground Always 10 kΩ or higher
      G24-10 (VC5) - Body ground Always 10 kΩ or higher
      G84-24 (AGND) - Body ground Always 10 kΩ or higher
      G24-6 (AGND) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  2. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. Reconnect the G24 engine switch and G84 certification ECU (smart key ECU assembly) connector.

    2. A01QRRDC06
      *a

      Component with harness connected

      (Engine Switch)

      Using an oscilloscope, check the waveform.

      Tech Tips

      Perform this inspection on the engine switch side.

      Measurement Condition
      Item Content
      Tester Connection G24-10 (VC5) - G24-6 (AGND)
      Tool Setting 2 V/DIV., 200 ms./DIV.
      Condition Engine switch off, key not in cabin, within 30 seconds after engine switch pressed
      OK
      Waveform is output normally (refer to illustration).
      Result
      Proceed to
      OK (for 2AR-FE)
      OK (for 3ZR-FAE)
      OK (for 3ZR-FE)
      OK (for 1AD-FTV)
      OK (for 2AD-FTV)
      OK (for 2AD-FHV)
      NG

    OK (for 2AR-FE)

    REPLACE ENGINE SWITCH Click here

    OK (for 3ZR-FAE)

    REPLACE ENGINE SWITCH Click here

    OK (for 3ZR-FE)

    REPLACE ENGINE SWITCH Click here

    OK (for 1AD-FTV)

    REPLACE ENGINE SWITCH Click here

    OK (for 2AD-FTV)

    REPLACE ENGINE SWITCH Click here

    OK (for 2AD-FHV)

    REPLACE ENGINE SWITCH Click here

    NG

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)