LIN COMMUNICATION SYSTEM, Diagnostic DTC:B278C

DTC Code DTC Name
B278C Lost Communication with Power Source Control

DESCRIPTION

This DTC is stored when LIN communication between the certification ECU (smart key ECU assembly) and power management control ECU stops for 10 seconds or more.

DTC No. Detection Item DTC Detection Condition Trouble Area
B278C Lost Communication with Power Source Control No communication between the certification ECU (smart key ECU assembly) and power management control ECU for 10 seconds or more.

  • Power management control ECU

  • Certification ECU (smart key ECU assembly)

  • Wire harness or connector

  • AM2 fuse

WIRING DIAGRAM

A0139ZEE01
*a Certification ECU (Smart Key ECU Assembly)
*b Power Management Control ECU
*c LIN Communication Line

CAUTION / NOTICE / HINT

Note


  • Inspect the fuses for circuits related to this system before performing the following procedure.

  • If the certification ECU (smart key ECU assembly) or power management control ECU is replaced, refer to Service Bulletin.

PROCEDURE


  1. CHECK DTC OUTPUT


    1. Clear the DTCs.

      Click here


      Body Electrical > Entry&Start > Clear DTCs

    2. Recheck for DTCs.


      Body Electrical > Entry&Start > Trouble Codes

      Tech Tips

      When DTC B278C and B2785 are output simultaneously, perform troubleshooting for DTC B2785 first.

      Result
      Result Proceed to
      Only B278C is output A
      DTC B278C and B2785 are output simultaneously B

    B

    GO TO DTC B2785 Click here

    A

  2. CHECK HARNESS AND CONNECTOR (POWER MANAGEMENT CONTROL ECU - AUXILIARY BATTERY, BODY GROUND)


    1. Disconnect the E111 and E112 power management control ECU connectors.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      E112-7 (AM21) - E111-6 (E1) Power switch off 11 to 14 V
      E111-1 (AM22) - E111-6 (E1) Power switch off 11 to 14 V

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      E111-6 (E1) - Body ground Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - POWER MANAGEMENT CONTROL ECU)


    1. Disconnect the E116 certification ECU (smart key ECU assembly) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      E112-11 (LIN2) - E116-12 (LIN) Always Below 1 Ω
      E112-11 (LIN2) - Body ground Always 10 kΩ or higher
      E116-12 (LIN) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. REPLACE POWER MANAGEMENT CONTROL ECU


    1. Replace the power management control ECU.

      for LHD: Click here

      for RHD: Click here

      Result
      Proceed to
      NEXT

    NEXT

  5. CHECK DTC OUTPUT


    1. Clear the DTCs.

      Click here


      Body Electrical > Entry&Start > Clear DTCs

    2. Recheck for DTCs.


      Body Electrical > Entry&Start > Trouble Codes
      OK
      DTC B278C is not output.
      Result
      Proceed to
      OK
      NG

    OK

    END (POWER MANAGEMENT CONTROL ECU WAS DEFECTIVE)

    NG

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)