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ENTRY AND START SYSTEM(for Start Function), Diagnostic DTC:B278A

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DTC Code DTC Name
B278A Short to GND in Immobiliser System Power Source Circuit
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DESCRIPTION

When there is a short to GND in the power supply for the transponder key amplifier of the power 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 Short to GND detected in the power supply of the transponder key amplifier of the power switch (VC5 - VC5) (1 trip detection logic*).

  • Harness or connector

  • Power switch

  • Certification ECU (smart key ECU assembly)
  • DTC Output Confirmation Operation:

  • With the shift state park (P) and the electrical key transmitter sub-assembly held near the power switch, a hybrid control system start operation is performed by pressing and holding the power switch when the transmitter battery is depleted.

Table 1. Vehicle Condition and Fail-safe Operation when Malfunction Detected
Vehicle Condition when Malfunction Detected Fail-safe Operation when Malfunction Detected
Hybrid control system cannot be started when transmitter battery is depleted by holding electrical key transmitter sub-assembly near power switch and pressing and holding power switch with shift state park (P). -
Table 2. Related Data List and Active Test
DTC No. Data List and Active Test
B278A -
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WIRING DIAGRAM

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CAUTION / NOTICE / HINT

Note:

  • When using the GTS with the power 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. 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 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 entry and start system (for Start Function) after confirming that the communication systems are functioning properly.

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

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

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PROCEDURE


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    CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. B004WZMC87
      *a

      Component with harness connected

      (Power Switch)

      		 *b Waveform

      Using an oscilloscope, check the waveform.

      Tip:

      Perform this inspection on the push power switch side.

      OK
      Tester Connection Condition Tool Setting Specified Condition
      A-10 (VC5) - A-6 (AGND) Power switch off, electrical key transmitter sub-assembly not in cabin, within 30 seconds after power switch pressed 2 V/DIV., 200 ms./DIV.

      Pulse generation

      (See waveform)
      Result
      Proceed to
      OK
      NG

  2. Click here

    CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - POWER SWITCH)


    1. Disconnect the G71 certification ECU (smart key ECU assembly) connector.

    2. Disconnect the A power switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      G71-7 (VC5) - A-10 (VC5) Always Below 1 Ω
      G71-7 (VC5) or A-10 (VC5) - Other terminals and body ground Always 10 kΩ or higher
      G71-11 (AGND) - A-6 (AGND) Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    • OKClick here
    • NG

      REPAIR OR REPLACE HARNESS OR CONNECTOR

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    CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. Reconnect the G71 certification ECU (smart key ECU assembly) connector.

    2. Reconnect the A power switch connector.

    3. B004SEDC54
      *a

      Component with harness connected

      (Certification ECU (Smart Key ECU Assembly))

      		 - -

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      G71-7 (VC5) - G71-11 (AGND) Power 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 POWER SWITCHClick here

    • NG

      REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)