ENGINE IMMOBILISER 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 power 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 power switch (VC5 - VC5) (1 trip detection logic*).

  • Wire harness or connector


  • Power switch


  • Certification ECU (smart key ECU assembly)

 With the shift lever in P, the key held near the power switch and a hybrid control system start operation is performed by pressing and holding the power 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
Hybrid control system cannot be started when key battery is depleted by holding key near power switch and pressing and holding power switch with shift lever in P -
Related Data List and Active Test
DTC Code Data List and Active Test
B278A -

WIRING DIAGRAM

A005AB8E05
*a Power Switch
*b Certification ECU (Smart Key ECU Assembly)

CAUTION / NOTICE / HINT

Note


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

  • 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 CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. Reconnect the L197 certification ECU (smart key ECU assembly) connectors.

    2. Reconnect the L194 power switch connector.

    3. A005B3ME02
      Text in Illustration
      *a

      Component with harness connected

      (Power Switch)

      Using an oscilloscope, check the waveform.

      Tech Tips

      Perform this inspection on the power switch side.

      Measurement Condition
      Item Content
      Tester Connection L194-10 (VC5) - L194-6 (AGND)
      Tool Setting 2 V/DIV., 200 ms./DIV.
      Condition Power switch off, key not in cabin, within 30 seconds after power switch pressed
      OK
      Waveform is output normally (refer to illustration).

    OK

    REPLACE POWER SWITCH Click here

    NG

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


    1. Disconnect the L197 certification ECU (smart key ECU assembly) connectors.

    2. Disconnect the L194 power switch connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      L197-1 (VC5) - L194-10 (VC5) Always Below 1 Ω
      L197-24 (AGND) - L194-6 (AGND) Always Below 1 Ω
      L194-10 (VC5) or L194-6 (AGND) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. Reconnect the L197 certification ECU (smart key ECU assembly) connector.

    2. Reconnect the L194 power switch connector.

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

      A005C0JE02
      Text in Illustration
      *a

      Component with harness connected

      (Certification ECU (Smart Key ECU Assembly))

      		 - -
      Standard Voltage
      Tester Connection Condition Specified Condition
      L197-1 (VC5) - L197-24 (AGND) Power switch off, brake pedal not depressed, 30 seconds or more after driver door opened and then closed Below 1 V

    OK

    REPLACE POWER SWITCH Click here

    NG

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)