DTC B2785: LIN Communication

DTC detecting condition:

When LIN communication error is detected 3 times in a row.

(Communication cannot be received because a problem occurs such as a series of noise continuously generated in LIN communication bus during power supply or ground short circuit in LIN communication bus)

Trouble symptom:

The keyless access function may not be operable.

Wiring diagram:

Keyless access with push button start system. Refer to WIRING SYSTEM (IMPREZA MODEL)>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM . Refer to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM . Refer to WIRING SYSTEM (CROSSTREK MODEL (HEV))>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

For replacement procedure of keyless access control module, steering lock control module and ID code box, refer to "REGISTRATION INSTRUCTIONS FOR IMMOBILIZER" provided as a separate volume.
Before performing diagnosis, refer to "CAUTION" in "General Description". Refer to KEYLESS ACCESS WITH PUSH BUTTON START (DIAGNOSTICS)>GENERAL DESCRIPTION>CAUTION .

CHECK DTC.
1. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start]. Refer to COMMON (DIAG)>CLEAR MEMORY .
2. Read the DTC of [Keyless Access with Push Button Start] using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START (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.
CHECK HARNESS (BETWEEN KEYLESS ACCESS control module AND STEERING LOCK control module).
1. Disconnect the ground terminal from battery.
2. Disconnect the keyless access control module connector.
3. Disconnect the steering lock control module connector.
4. Using the tester, measure the resistance between terminals.
  Connector & terminal
  
  (i241) No. 20 - (i47) No. 5:
Is the resistance less than 1 Ω?

Yes: Go to 3.

No: Repair or replace the open circuit of harness.
CHECK HARNESS (GROUND SHORT CIRCUIT).
Using a tester, measure the resistance between the keyless access control module connector or steering lock control module connector and chassis ground.

Connector & terminal

(i241) No. 20 - Chassis ground:

(i47) No. 5 - Chassis ground:

Is the resistance 10 kΩ or more?

Yes: Go to 4.

No: Repair or replace the short circuit of the harness.
CHECK HARNESS (SHORT CIRCUIT TO POWER SUPPLY).
Using a tester, measure the voltage between the keyless access control module connector or steering lock control module connector and chassis ground.

Connector & terminal

(i241) No. 20 - Chassis ground:

(i47) No. 5 - Chassis ground:

Is the voltage 1 V or less?

Yes: Go to 5.

No: Repair or replace the short circuit of the harness.
CHECK HARNESS (BETWEEN KEYLESS ACCESS control module AND ID CODE BOX).
1. Disconnect the ID code box connector.
2. Using the tester, measure the resistance between terminals.
  Connector & terminal
  
  (i241) No. 20 - (i33) No. 2:
Is the resistance less than 1 Ω?

Yes: Go to 6.

No: Repair or replace the open circuit of harness.
CHECK KEYLESS ACCESS control module.
1. Connect the keyless access control module connector.
2. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start]. Refer to COMMON (DIAG)>CLEAR MEMORY .
3. Read the DTC of [Keyless Access with Push Button Start] using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START (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 7.
CHECK STEERING LOCK control module.
1. Connect the steering lock control module connector.
2. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start]. Refer to COMMON (DIAG)>CLEAR MEMORY .
3. Read the DTC of [Keyless Access with Push Button Start] using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START (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:
  - For C5 model, Go to 8.
  - For models except for C5 model, 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.
CHECK ID CODE BOX.
1. Connect the ID code box connector.
2. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start]. Refer to COMMON (DIAG)>CLEAR MEMORY .
3. Read the DTC of [Keyless Access with Push Button Start] using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START (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: 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.