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

Toyota Tacoma (2015-2018) Service Manual: 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

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) ).
  • 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 ).
  • 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.

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

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
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

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. ).

(c) Recheck for DTCs.

Result

Proceed to

DTC B2785 is output

A

DTC B2785 is not output

B
A

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

B

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

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