ENGINE 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 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).

  • Harness or connector


  • Engine switch


  • Certification ECU (smart key ECU assembly)

 With the shift lever in P*2, the electrical key transmitter sub-assembly is held against the engine switch and an engine start operation is performed by pressing and holding the engine switch when the transmitter 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 transmitter battery is depleted by holding electrical key transmitter sub-assembly against 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

A004JS8E43
*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 entry and start system (for Entry Function) 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 HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - ENGINE SWITCH)


    1. Disconnect the D41 certification ECU (smart key ECU assembly) connector.

    2. Disconnect the D25 engine switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      D41-1 (VC5) - D25-10 (VC5) Always Below 1 Ω
      D41-24 (AGND) - D25-6 (AGND) Always Below 1 Ω
      D41-1 (VC5) - Body ground Always 10 kΩ or higher
      D41-24 (AGND) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  2. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. Reconnect the D41 certification ECU (smart key ECU assembly) connector.

    2. Reconnect the D25 engine switch connector.

    3. A004HEZE02
      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 D25-10 (VC5) - D25-6 (AGND)
      Tool Setting 2 V/DIV., 200 ms./DIV.
      Condition Engine switch off, key not inside vehicle, and within 30 seconds after engine switch pushed
      OK
      Waveform is output normally (refer to illustration).

    OK

    REPLACE ENGINE SWITCH Click here

    NG

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)