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.

  • *1: Only output while a malfunction is present.

  • *2: for CVT

  • *3: for Multi-Mode Manual Transaxle

Table 1. 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

-

  • *1: for CVT

  • *2: for Multi-Mode Manual Transaxle

Table 2. Related Data List and Active Test

DTC No.

Data List and Active Test

B278A

-

WIRING DIAGRAM

B329423E02

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. B271009C04

      *a

      Component with harness connected

      (Engine Switch)

      Using an oscilloscope, check the waveform.

      Tip:

      Perform this inspection on the engine switch side.

      Table 3. 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

    NG

    E
    A

    REPLACE ENGINE SWITCH

    Click here

    B

    REPLACE ENGINE SWITCH

    Click here

    C

    REPLACE ENGINE SWITCH

    Click here

    D

    REPLACE ENGINE SWITCH

    Click here

    E

  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