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: 

Immobilizer system Ref. to WIRING SYSTEM>IMMOBILIZER SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC. 
   1. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
   2. Read the DTC of [Keyless Access with Push Button Start] using the Subaru Select Monitor. Ref. 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.
2. CHECK HARNESS (BETWEEN KEYLESS ACCESS CONTROL MODULE AND STEERING LOCK CONTROL MODULE). 
   1. Disconnect the ground terminal from battery sensor. Ref. to REPAIR CONTENTS>NOTE>BATTERY .
   2. Disconnect the keyless access Control Module connector.
   3. Disconnect the steering lock Control Module connector.
   4. For model with ID code box, disconnect the ID code box connector.
   5. Using a tester, measure the resistance between the keyless access Control Module connector and steering lock Control Module connector.

      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.

3. 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.

4. 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:  For model with ID code box. Go to  5. For model without ID code box. Go to  6.

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

5. CHECK HARNESS (BETWEEN KEYLESS ACCESS CONTROL MODULE AND ID CODE BOX). 

   Using a tester, measure the resistance between the keyless access Control Module connector and the ID code box connector.

   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.

6. 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]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
   3. Read the DTC of [Keyless Access with Push Button Start] using the Subaru Select Monitor. Ref. 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. Ref. to SECURITY AND LOCKS>KEYLESS ACCESS CONTROL MODULE .

   No:  Go to  7.

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]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
   3. Read the DTC of [Keyless Access with Push Button Start] using the Subaru Select Monitor. Ref. 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. Ref. to SECURITY AND LOCKS>STEERING LOCK CONTROL MODULE .

   No: 

   • For model with ID code box. Go to  8.
   • For model without ID code box, 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.
8. 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]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
   3. Read the DTC of [Keyless Access with Push Button Start] using the Subaru Select Monitor. Ref. to KEYLESS ACCESS WITH PUSH BUTTON START (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B2785 displayed? (Current malfunction)

   Yes:  Replace the ID code box. Ref. 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.