NETWORKING: LIN COMMUNICATION SYSTEM (except TMC Made): B2785; Communication Malfunction between ECUs Connected by LIN; 2023 MY Corolla Corolla Hatchback Corolla HV GR Corolla [09/2022

Last Modified: 05-13-2024	6.11:8.1.0	Doc ID: RM1000000026D5Y
Model Year Start: 2023	Model: GR Corolla	Prod Date Range: [09/2022 - 11/2022]
Title: NETWORKING: LIN COMMUNICATION SYSTEM (except TMC Made): B2785; Communication Malfunction between ECUs Connected by LIN; 2023 MY Corolla Corolla Hatchback Corolla HV GR Corolla [09/2022 - 11/2022]

DTC

B2785

Communication Malfunction between ECUs Connected by LIN

DESCRIPTION

If the certification ECU (smart key ECU assembly) detects a communication error with an ECU connected to the certification bus lines for 7 seconds or more, DTC B2785 will be stored.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
B2785	Communication Malfunction between ECUs Connected by LIN	Errors in LIN communication between ECUs or an open or short in communication lines. The certification ECU (smart key ECU assembly) detects a communication error with an ECU connected to the certification bus lines for 7 seconds or more.	Certification ECU (smart key ECU assembly) Steering lock ECU (steering lock actuator or upper bracket assembly) ID code box (immobiliser code ECU) Wire harness or connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Before performing the inspection, check that DTC B2786, B2789 or B278C is not output.
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When using the Techstream with the power switch off, connect the Techstream to the DLC3 and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the Techstream and the vehicle begins. Then select Model Code "KEY REGIST" under manual mode and enter the following menus: Body Electrical / Smart Key. While using the Techstream, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the Techstream and the vehicle.
Before replacing the certification ECU (smart key ECU assembly), ID code box (immobiliser code ECU) or steering lock ECU (steering lock actuator or upper bracket assembly), refer to Registration.
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PROCEDURE

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

(a) Disconnect the I1 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the I59 steering lock ECU (steering lock actuator or upper bracket assembly) connector.

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

NOTICE:

Make sure that each ECU is in sleep mode before performing the inspection. To enter sleep mode, turn the power switch from on (IG) to off and wait for 180 seconds or more without operating any switches.

Standard Resistance:

Tester Connection	Condition	Specified Condition
I1-14 (LIN) - I59-5 (LIN)	Power switch off	Below 1 Ω
I1-14 (LIN) - I20-2 (LIN1)	Power switch off	Below 1 Ω
I1-14 (LIN), I59-5 (LIN) or I20-2 (LIN1) - Body ground	Power switch off	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

2.	CHECK FOR DTC (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY))

(a) Connect the I1 certification ECU (smart key ECU assembly) connector.

(b) Connect the I20 ID code box (immobiliser code ECU) connector.

Body Electrical > Smart Key > Clear DTCs

(d) Recheck for DTCs.

Body Electrical > Smart Key > Trouble Codes

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

REPLACE STEERING LOCK ECU (STEERING LOCK ACTUATOR OR UPPER BRACKET ASSEMBLY)

3.	CHECK FOR DTC (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY))

(a) Connect the I59 steering lock ECU (steering lock actuator or upper bracket assembly) connector.

(b) Disconnect the I20 ID code box (immobiliser code ECU) connector.

Body Electrical > Smart Key > Clear DTCs

(d) Recheck for DTCs.

Body Electrical > Smart Key > Trouble Codes

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

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

REPLACE ID CODE BOX (IMMOBILISER CODE ECU)