LIN COMMUNICATION SYSTEM, Diagnostic DTC:B2785

DTC Code DTC Name
B2785 Communication Malfunction between ECUs Connected by LIN

DESCRIPTION

The certification ECU (smart key ECU assembly) monitors communication between all the ECUs connected to the certification bus lines. When the certification ECU (smart key ECU assembly) detects errors in communication with all the ECUs connected to the certification bus lines at a set interval and 3 times in a row, DTC B2785 will be stored.

DTC No. DTC Detection Condition Trouble Area
B2785

  • Errors in LIN communication between ECUs or an open or short in communication lines

  • LIN communication from the certification ECU (smart key ECU assembly) detects errors in communication 3 times in a row.

  • Certification ECU (smart key ECU assembly)

  • Power management control ECU

  • Transmission control ECU assembly

  • ID code box (immobiliser code ECU)

  • Wire harness or connector

WIRING DIAGRAM

A003W2BE36

INSPECTION PROCEDURE

Note


  • If the certification ECU (smart key ECU assembly) is replaced, register the key.

  • If the transmission control ECU assembly is replaced, register the ECU code.

  • If the ID code box (immobiliser code ECU) is replaced, register the ECU code and ECU communication ID.

  • When using the intelligent tester to troubleshoot with the power switch off:

    Connect the intelligent tester to the DLC3, and turn the courtesy switch on and off at 1.5-second intervals until communication between the intelligent tester and vehicle begins.

PROCEDURE


  1. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - EACH ECU)


    1. Disconnect the H1*1, H143*2, H4, H22 and A22 connectors.


      • *1: w/ Entry Function

      • *2: w/o Entry Function

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

      Standard Resistance
      w/ Entry Function
      Tester Connection Condition Specified Condition
      H1-29 (LIN) - A22-24 (LIN) Always Below 1 Ω
      H1-29 (LIN) - H4-11 (LIN2) Always Below 1 Ω
      H1-29 (LIN) - H22-3 (LIN1) Always Below 1 Ω
      H1-29 (LIN) - Body ground Always 10 kΩ or higher
      w/o Entry Function
      Tester Connection Condition Specified Condition
      H143-29 (LIN) - A22-24 (LIN) Always Below 1 Ω
      H143-29 (LIN) - H4-11 (LIN2) Always Below 1 Ω
      H143-29 (LIN) - H22-3 (LIN1) Always Below 1 Ω
      H143-29 (LIN) - Body ground Always 10 kΩ or higher
      Standard Voltage
      w/ Entry Function
      Tester Connection Condition Specified Condition
      H1-29 (LIN) - Body ground Always Below 1 V
      w/o Entry Function
      Tester Connection Condition Specified Condition
      H143-29 (LIN) - Body ground Always Below 1 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  2. CHECK DTC OUTPUT (TRANSMISSION CONTROL ECU ASSEMBLY)


    1. Reconnect the H1*1, H143*2, H4 and H22 connectors.


      • *1: w/ Entry Function

      • *2: w/o Entry Function

    2. Clear the DTC Click here.

    3. Recheck for DTCs.

      Result
      Result Proceed to
      DTC B2785 is output A
      DTC B2785 is not output B

    B

    REPLACE TRANSMISSION CONTROL ECU ASSEMBLY Click here

    A

  3. CHECK DTC OUTPUT (POWER MANAGEMENT CONTROL ECU)


    1. Reconnect the A22 connector.

    2. Disconnect the H4 connector.

    3. Clear the DTC Click here.

    4. Recheck for DTCs.

      Result
      Result Proceed to
      DTC B2785 is output A
      DTC B2785 is not output B

    B

    REPLACE POWER MANAGEMENT CONTROL ECU Click here

    A

  4. CHECK DTC OUTPUT (ID CODE BOX (IMMOBILISER CODE ECU))


    1. Reconnect the H4 connector.

    2. Disconnect the H22 connector.

    3. Clear the DTC Click here.

    4. Recheck for DTCs.

      Result
      Result Proceed to
      DTC B2785 is output A
      DTC B2785 is not output B

    B

    REPLACE ID CODE BOX (IMMOBILISER CODE ECU)

    A

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)