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*1).

  • Engine switch

  • Wire harness or connector

  • Certification ECU (smart key ECU assembly)

DTC output confirmation operation:


  • With the shift lever in P*2 or N*3 and the key held near the engine switch, 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*1 or N*2 -

Related Data List and Active Test
DTC No. Data List and Active Test
B278A -

WIRING DIAGRAM

A01TBL6E02
*a Engine Switch
*b Certification ECU (Smart Key ECU Assembly)

CAUTION / NOTICE / HINT

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. Reconnect the E36 engine switch and E35 certification ECU (smart key ECU assembly) connectors.

    2. A01T984C04
      *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 E36-10 (VC5) - E36-6 (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.
      Result
      Result Proceed to
      OK (1NR-FE) A
      OK (1ZR-FAE) B
      OK (1ND-TV) C
      OK (1AD-FTV) D
      OK (1ZR-FE) E
      OK (2ZR-FE) F
      NG G

    A

    REPLACE ENGINE SWITCH except Sedan: Click here
    REPLACE ENGINE SWITCH for Sedan: Click here

    B

    REPLACE ENGINE SWITCH except Sedan: Click here
    REPLACE ENGINE SWITCH for Sedan: Click here

    C

    REPLACE ENGINE SWITCH except Sedan: Click here
    REPLACE ENGINE SWITCH for Sedan: Click here

    D

    REPLACE ENGINE SWITCH Click here

    E

    REPLACE ENGINE SWITCH Click here

    F

    REPLACE ENGINE SWITCH Click here

    G

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


    1. Disconnect the E35 certification ECU (smart key ECU assembly) connector.

    2. Disconnect the E36 engine switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      E35-1 (VC5) - E36-10 (VC5) Always Below 1 Ω
      E35-24 (AGND) - E36-6 (AGND) Always Below 1 Ω
      E36-10 (VC5) - Body ground Always 10 kΩ or higher
      E35-1 (VC5) - Body ground Always 10 kΩ or higher
      E36-6 (AGND) - Body ground Always 10 kΩ or higher
      E35-24 (AGND) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE CERTIFICATION ECU (SMART KEY ASSEMBLY)

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR