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. DTC Detection Condition Trouble Area
B278C 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

WIRING DIAGRAM

A0005BQE21
*a from Auxiliary Battery
*b Certification ECU (Smart Key ECU Assembly)
*c Power Management Control ECU
*d LIN Communication Line

CAUTION / NOTICE / HINT

Note


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

    2. Recheck for DTCs.

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

      Tech Tips

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


    B

    GO TO DTC B2785 Click here

    A

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


    1. Disconnect the H1 and H2 power management control ECU connectors.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      H1-6 (E1) - Body ground Always Below 1 Ω
      Standard Voltage
      Tester Connection Condition Specified Condition
      H1-1 (AM22) - Body ground Power switch off 11 to 14 V
      H2-7 (AM21) - Body ground Power switch off 11 to 14 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

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


    1. Disconnect the H58 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
      H58-12 (LIN) - H2-11 (LIN2) Always Below 1 Ω
      H58-12 (LIN) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. REPLACE POWER MANAGEMENT CONTROL ECU


    1. Replace the power management control ECU Click here.


    NEXT

  5. CHECK DTC OUTPUT


    1. Clear the DTCs Click here.

    2. Recheck for DTCs.

      OK
      DTC B278C is not output.

    OK

    END (POWER MANAGEMENT CONTROL ECU WAS DEFECTIVE)

    NG

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)