DTC    B2785    Communication Malfunction between ECUs Connected by LIN

for Preparation Click here


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
  1. Errors in LIN communication between ECUs or an open or short in communication lines
  2. LIN communication from the certification ECU (smart key ECU assembly) detects errors in communication 3 times in a row.
  1. Certification ECU (smart key ECU assembly)
  2. Power management control ECU
  3. Transmission control ECU assembly
  4. ID code box (immobiliser code ECU)
  5. Wire harness or connector

WIRING DIAGRAM


B203743E36


INSPECTION PROCEDURE

NOTICE:
  1. If the certification ECU (smart key ECU assembly) is replaced, register the key.
  2. If the transmission control ECU assembly is replaced, register the ECU code.
  3. If the ID code box (immobiliser code ECU) is replaced, register the ECU code and ECU communication ID.
  4. 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.

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

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

    1. *1: w/ Entry Function
    2. *2: w/o Entry Function

  1. 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. *1: w/ Entry Function
    2. *2: w/o Entry Function

  1. Clear the DTC (Click here).

  1. 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.

  1. Disconnect the H4 connector.

  1. Clear the DTC (Click here).

  1. 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.

  1. Disconnect the H22 connector.

  1. Clear the DTC (Click here).

  1. 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)