SMART ENTRY AND START SYSTEM(for Start Function), 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) detected. (1 trip detection logic*)

  • Engine switch

  • Certification ECU (smart key ECU assembly)

  • Wire harness or connector

DTC output confirmation operation:


  • With the shift lever in P and the electrical key transmitter sub-assembly held near the engine switch, 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 transmitter near engine switch and pressing and holding engine switch with shift lever in P -
Related Data List and Active Test
DTC No. Data List and Active Test
B278A -

WIRING DIAGRAM

B006WTHE01
*a CODE
*b Engine Switch
*c 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.

  • The smart entry and start system (for Start Function) uses the LIN communication system and CAN communication system. Inspect the communication function by following How to Proceed with Troubleshooting. Troubleshoot the smart entry and start system (for Start Function) after confirming that the communication systems are functioning properly.

    Click here

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

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

PROCEDURE


  1. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. Using an oscilloscope, check the waveform.

      B006YAPC69
      *a

      Component with harness connected

      (Engine Switch)

      		 - -

      Tech Tips

      Perform this inspection on the engine switch side.

      OK
      Tester Connection Condition Tool Setting Specified Condition
      K63-10 (VC5) - K63-6 (AGND) Engine switch off, electrical key transmitter sub-assembly not in cabin, within 30 seconds of engine switch pressed 2 V/DIV., 200 ms./DIV. Pulse generation
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE ENGINE SWITCH for A25A-FKS: Click here
    REPLACE ENGINE SWITCH for 2GR-FKS: Click here
    REPLACE ENGINE SWITCH for 2AR-FE: Click here

    NG

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


    1. Disconnect the K62 certification ECU (smart key ECU assembly) connector.

    2. Disconnect the K63 engine switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      K62-7 (VC5) - K63-10 (VC5) Always Below 1 Ω
      K62-11 (AGND) - K63-6 (AGND) Always Below 1 Ω
      K62-7 (VC5) or K63-10 (VC5) - Other terminals and body ground Always 10 kΩ or higher
      K62-11 (AGND) or K63-6 (AGND) - Other terminals and body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. Connect the K62 certification ECU (smart key ECU assembly) connector.

    2. Connect the K63 engine switch connector.

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

      B0071CSC28
      *a

      Component with harness connected

      (Certification ECU (Smart Key ECU Assembly))

      		 - -
      Standard Voltage
      Tester Connection Condition Specified Condition
      K62-7 (VC5) - K62-11 (AGND) Engine switch off, brake pedal not depressed, 30 seconds or more after driver door opened and then closed Below 1 V
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE ENGINE SWITCH for A25A-FKS: Click here
    REPLACE ENGINE SWITCH for 2GR-FKS: Click here
    REPLACE ENGINE SWITCH for 2AR-FE: Click here

    NG

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)