Toyota Tacoma (2015-2018) Service Manual: Communication Malfunction between ECUs Connected by LIN (B2785)

Toyota Tacoma (2015-2018) Service Manual / Multiplex Communication / Lin Communication System / Communication Malfunction between ECUs Connected by LIN (B2785)

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) Steering lock ECU (steering lock actuator or upper bracket assembly) Wire harness or connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

If the certification ECU (smart key ECU assembly) is replaced, register the keys (See page ).
If the steering lock ECU (steering lock actuator or upper bracket assembly) is replaced, register the ECU code (See page ).
When using the Techstream with the vehicle ignition switch off, connect the Techstream to the vehicle 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 the vehicle type under manual mode and enter the following menus: Body Electrical / Smart Access. 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.

PROCEDURE

1.	CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - STEERING LOCK ECU (STEERING LOCK ACTUATOR OR UPPER BRACKET ASSEMBLY))

(a) Disconnect the C29 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the S45 steering lock ECU (steering lock actuator or upper bracket assembly) connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
C29-6 (LIN) - S45-5 (LIN)	Always	Below 1 Ω
C29-6 (LIN) or S45-5 (LIN) - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

2.	CHECK DTC OUTPUT (STEERING LOCK ECU (STEERING LOCK ACTUATOR OR UPPER BRACKET ASSEMBLY))

(a) Reconnect the C29 certification ECU (smart key ECU assembly) connector.

(b) Clear the DTCs (See page (c) Recheck for DTCs. ).

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

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

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

Dtc Check / Clear

DTC CHECK / CLEAR 1. CHECK DTC (a) Connect the Techstream to the DLC3. (b) Turn the ignition switch to ON. (c) Turn the Techstream on. (d) Enter the following menus: Body Electrical / Smart Acces ...

No Response from Steering Lock ECU (B2786)

DESCRIPTION This DTC is stored when LIN communication between the certification ECU (smart key ECU assembly) and steering lock ECU (steering lock actuator or upper bracket assembly) stops for 10 ...

Other materials:

Low Power Supply Voltage Malfunction (C1241)
DESCRIPTION If there is a problem with the skid control ECU (master cylinder solenoid) power supply circuit, the skid control ECU outputs the DTC and prohibits operation under the fail-safe function. If the voltage supplied to terminal IG1 is not within the DTC detection threshold due to mal ...

Unable to Unlock Steering Wheel (Engine cannot Start)
DESCRIPTION The steering lock actuator assembly activates the steering lock motor and moves the lock bar into the steering column to lock the steering. The steering may not unlock when the lock bar gets stuck in the lock hole of the steering column. In this case, if the engine switch is turned ...

Power Source Circuit
DESCRIPTION This circuit provides power to operate the forward recognition camera. WIRING DIAGRAM CAUTION / NOTICE / HINT NOTICE: Inspect the fuses for circuits related to this system before performing the following inspection procedure. PROCEDURE 1. CHECK HARNESS A ...