DTC B2785: Communication Malfunction between ECUs Connected by LIN: Procedure

WARNING: This page is about a different car, the 2011 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.

RECONFIRM DTC
1. Clear the DTC and repeat the procedure to re-check it. Refer to DTC CHECK / CLEAR .
  OK
  
  DTC is not output.
OK → END (SYSTEM IS NORMAL)

NG: Go to next step

CHECK WIRE HARNESS (CERTIFICATION ECU - ID CODE BOX - POWER SOURCE CONTROL ECU)

Disconnect the D14, D39 and D44 ECU connectors.

Fig 1: Identifying D14, D39 And D44 ECU Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Disconnect the D29 ID code box connector.

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

Resistance

Tester Connection	Condition	Specified Condition
D14-5 (LIN) - D29-3 (LIN)	Always	Below 1 Ω
D14-5 (LIN) - D44-30 (LIN1)	Always	Below 1 Ω
D14-5 (LIN) - D39-10 (LIN)	Always	Below 1 Ω
D14-5 (LIN) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: Go to next step

REPLACE CERTIFICATION ECU (CHECK OPERATION OF CERTIFICATION ECU)
1. Replace the certification ECU.
2. Clear the DTC and repeat the procedure to re-check it. Refer to DTC CHECK / CLEAR .
  OK
  
  DTC is not output.
OK → END (CERTIFICATION ECU IS DEFECTIVE)

NG: Go to next step
REPLACE POWER SOURCE CONTROL ECU (CHECK OPERATION OF POWER SOURCE CONTROL ECU)
1. Replace the power source control ECU.
2. Clear the DTC and repeat the procedure to re-check it. Refer to DTC CHECK / CLEAR .
  OK
  
  DTC is not output.
OK → END (POWER SOURCE CONTROL ECU IS DEFECTIVE)

NG: Go to next step
REPLACE STEERING LOCK ECU (CHECK OPERATION OF STEERING LOCK ECU)
1. Replace the steering lock ECU.
2. Clear the DTC and repeat the procedure to re-check it. Refer to DTC CHECK / CLEAR .
  OK
  
  DTC is not output.
OK → END (STEERING LOCK ECU IS DEFECTIVE)

NG → REPLACE ID CODE BOX