Toyota CH-R Service Manual: Communication Malfunction between ECUs Connected by LIN (B2785)

Toyota CH-R Service Manual / Networking / Lin Communication System / Communication Malfunction between ECUs Connected by LIN (B2785)

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

Any of the following conditions is met:

  • Errors in LIN communication between ECUs.
  • Open in communication lines.
  • 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
  • AM2 fuse
  • STRG LOCK fuse
  • ECU-B NO. 1 fuse
DTC Detection Conditions
 

Vehicle Condition

Pattern 1

Pattern 2

Pattern 3

Pattern 4

Diagnosis Condition

-

○

○

○

○

Malfunction Status

Errors in LIN communication between ECUs

○

-

-

-

Open in communication lines

-

○

-

-

Short in communication lines

-

-

○

-

The certification ECU (smart key ECU assembly) detects a communication error with an ECU connected to the certification bus lines

-

-

-

○

Detection Time

-

-

-

7 seconds or more

Number of Trips

1 trip

1 trip

1 trip

1 trip

HINT:

DTC will be output when conditions for either of the patterns in the table above are met.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • Before performing the inspection, check that DTC B2786, B2789 or B278C is not output.

    Click here

  • When using the Techstream with the ignition 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 the vehicle type 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.
  • If the certification ECU (smart key ECU assembly), ID code box (immobiliser code ECU) and steering lock ECU (steering lock actuator or upper bracket assembly) is replaced, refer to Registration.

    Click here

PROCEDURE

1.

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

(a) Disconnect the F1 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the F78 steering lock ECU (steering lock actuator or upper bracket assembly) connector.

(c) Disconnect the F21 ID code box (immobiliser code ECU) 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 ignition switch from ON to off and wait for 180 seconds or more without operating any switches.

Standard Resistance:

Tester Connection

Switch Condition

Specified Condition

F1-13 (LIN) - F21-2 (LIN1)

Ignition switch off

Below 1 Ω

F1-13 (LIN) - F78-5 (LIN)

Ignition switch off

Below 1 Ω

F1-13 (LIN), F78-5 (LIN) or F21-2 (LIN1) - Body ground

Ignition switch off

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

2.

CHECK FOR DTC (STEERING LOCK ECU (STEERING LOCK ACTUATOR OR UPR BRACKET ASSEMBLY))

(a) Reconnect the F1 certification ECU (smart key ECU assembly) connector.

(b) Reconnect the F21 ID code box (immobiliser code ECU) connector.

(c) Clear the DTCs.

Click here

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
B

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

A

3.

CHECK FOR DTC (ID CODE BOX (IMMOBILISER CODE ECU))

(a) Reconnect the F78 steering lock ECU (steering lock actuator or upper bracket assembly) connector.

(b) Disconnect the F21 ID code box (immobiliser code ECU) connector.

(c) Clear the DTCs.

Click here

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
A

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

B

REPLACE ID CODE BOX (IMMOBILISER CODE ECU)

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