Lexus NX: Communication Malfunction between ECUs Connected by LIN (B2785)

Lexus NX Service Manual / Power Source & Network / Networking / Lin Communication System / Communication Malfunction between ECUs Connected by LIN (B2785)

DESCRIPTION

The certification ECU intermittently monitors the LIN communication bus between the components related to certification. DTC B2785 is stored when a malfunction in the LIN communication bus between the components related to certification is detected 3 times consecutively.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B2785

Communication Malfunction between ECUs Connected by LIN

The certification ECU detects a malfunction in the LIN communication bus between components related to certification 3 times consecutively.

  • Certification ECU (smart key ECU assembly)
  • ID code box (immobiliser code ECU)
  • Steering lock actuator assembly
  • Harness or connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • When using the Techstream with the power switch off to troubleshoot:
  • Connect the Techstream to the vehicle, and turn a courtesy light switch on and off at 1.5 second intervals until communication between the Techstream and vehicle begins.
  • Before replacing the certification ECU (smart key ECU assembly), ID code box (immobiliser code ECU) or steering lock actuator assembly, refer to the engine immobiliser system.

PROCEDURE

1.

CLEAR DTC

(a) Clear the DTCs.

Click here

Body Electrical > Smart Access > Clear DTCs
NEXT

2.

CHECK FOR DTC

(a) Check for DTCs.

Click here

Body Electrical > Smart Access > Trouble Codes
DTC B2785 is not output

USE SIMULATION METHOD TO CHECK

DTC B2785 is output

3.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU [SMART KEY ECU ASSEMBLY] - ID CODE BOX [IMMOBILISER CODE ECU] OR STEERING LOCK ACTUATOR ASSEMBLY)

(a) Disconnect the I53 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the I26 ID code box (immobiliser code ECU) connector.

(c) Disconnect the I2 steering lock actuator assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I53-6 (LIN) - I2-5 (LIN)

Always

Below 1 Ω

I53-6 (LIN) - I26-2 (LIN1)

Always

Below 1 Ω

I53-6 (LIN) - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4.

CLEAR DTC

(a) Clear the DTCs.

Click here

Body Electrical > Smart Access > Clear DTCs
NEXT

5.

CHECK FOR DTC

(a) Disconnect the I2 steering lock actuator assembly connector.

(b) Check for DTCs.

Click here

Body Electrical > Smart Access > Trouble Codes
DTC B2785 is output

REPLACE STEERING LOCK ACTUATOR ASSEMBLY

DTC B2785 is not output

6.

CLEAR DTC

(a) Clear the DTCs.

Click here

Body Electrical > Smart Access > Clear DTCs
NEXT

7.

CHECK FOR DTC

(a) Disconnect the I26 ID code box (immobiliser code ECU) connector.

(b) Check for DTCs.

Click here

Body Electrical > Smart Access > Trouble Codes
DTC B2785 is not output

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

DTC B2785 is output

REPLACE ID CODE BOX (IMMOBILISER CODE ECU)

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