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

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*1).

  • Engine switch

  • Harness or connector

  • Certification ECU (smart key ECU assembly)

 With the shift lever in P, 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.

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

A01BHI8E02

INSPECTION PROCEDURE

Note


  • When using the GTS with the engine switch off, connect the GTS to the DLC3 and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the GTS and the vehicle begins. Then select Model Code "KEY REGIST" under manual mode and enter the following menus: Body Electrical / Entry & Start (CAN). While using the GTS, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the GTS and the vehicle.

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

  • After repair, confirm that no DTCs are output by performing "DTC Output Confirmation Operation."

PROCEDURE


  1. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. A01BCCFE13
      Text in Illustration
      *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 I32-10 (VC5) - I32-6 (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
      The waveform is similar to that shown in the illustration.

    NG

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

    OK

    REPLACE ENGINE SWITCH Click here

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


    1. Disconnect the B75 and B76 certification ECU (smart key ECU assembly) connectors.

    2. Disconnect the I32 engine switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      B76-20 (VC5) - I32-10 (VC5) Always Below 1 Ω
      B75-24 (AGND) - I32-6 (AGND) Always Below 1 Ω
      I32-10 (VC5) - Body ground Always 10 kΩ or higher
      B76-20 (VC5) - Body ground Always 10 kΩ or higher
      I32-6 (AGND) - Body ground Always 10 kΩ or higher
      B75-24 (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. Connect the B75 and B76 certification ECU (smart key ECU assembly) connectors.

    2. Connect the I32 engine switch connector.

      A01BFZWE02
      Text in Illustration
      *a

      Component with harness connector

      (Certification ECU [Smart Key ECU Assembly])

      		 - -

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      B76-20 (VC5) - B75-24 (AGND) Engine switch off, key not in cabin, within 30 seconds after engine switch pressed Below 1 V

    NG

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

    OK

    REPLACE ENGINE SWITCH Click here