DTC B2785: LIN Communication

DTC detecting condition: 

When LIN communication error is detected three consecutive times.

(Communication cannot be received due to faulty such as ongoing power supply short or ground short of LIN communication bus and consecutive noise occurrence to the LIN communication bus)

Trouble symptom: 

The keyless access function may not be operable.

Wiring diagram: 

Push button start system. Refer to WIRING SYSTEM>PUSH BUTTON START SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC. 
   1. Perform the clear memory for «Keyless Access with Push Button Start» using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>CLEAR MEMORY .
   2. Read DTCs of «Keyless Access with Push Button Start» using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Is DTC B2785 displayed? (Current malfunction)

      Yes:  Go to  2.

      No:  Even if DTC is displayed, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

      NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
2. CHECK HARNESS (OPEN CIRCUIT). 
   1. Disconnect the keyless access control module connector.
   2. Disconnect the steering lock control module connector.
   3. Disconnect the ID code box connector. (With ID code box)
   4. Using a tester, measure the resistance between the keyless access control module connector and the steering lock control module connector or the ID code box connector (with ID code box).

      Connector & terminal 

      (B574) No. 20 - (B424) No. 5:

      (B574) No. 20 - (B422) No. 2: (with ID code box)

      Is the resistance less than 1 Ω?

      Yes:  Go to  3.

      No:  Repair or replace the open circuit of harness.

3. CHECK HARNESS (GROUND SHORT CIRCUIT). 

   Using a tester, measure the resistance between the keyless access control module connector, the steering lock control module connector or the ID code box connector (with ID code box) and chassis ground.

   Connector & terminal 

   (B574) No. 20 - Chassis ground:

   (B424) No. 5 - Chassis ground:

   (B422) No. 2 - Chassis ground: (wit h ID c ode box)

   Is the resistance 10 kΩ or more?

   Yes:  Go to  4.

   No:  Repair or replace the short circuit of the harness.

4. CHECK DTC. 
   1. Connect the keyless access control module connector only.
   2. Read DTCs of «Keyless Access with Push Button Start» using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Is DTC B2785 displayed? (Current malfunction)

      Yes:  Replace the keyless access control module. Refer to SECURITY AND LOCKS>KEYLESS ACCESS control module .

      No:  Go to  5.

5. CHECK ID CODE BOX. 
   NOTE: For model without ID code box, go to the next step.
   1. Connect the ID code box.
   2. Read DTCs of «Keyless Access with Push Button Start» using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Is DTC B2785 displayed? (Current malfunction)

      Yes:  Replace the ID code box. Refer to SECURITY AND LOCKS>ID CODE BOX .

      No:  Go to  6.

6. CHECK STEERING LOCK control module. 
   1. Connect the steering lock control module.
   2. Perform the clear memory for «Keyless Access with Push Button Start» using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>CLEAR MEMORY .
   3. Read DTCs of «Keyless Access with Push Button Start» using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Is DTC B2785 displayed? (Current malfunction)

      Yes:  Replace the steering lock control module. Refer to SECURITY AND LOCKS>STEERING LOCK control module .

      No:  Even if DTC is displayed, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

      NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.