DTC B2789: ID Code Box Communication

DTC detecting condition: 

When the LIN transmission frame cannot be received for 10 consecutive seconds during the LIN bus Wake UP after being received once from the ID code box.

Trouble symptom: 

Engine will not start.

Wiring diagram: 

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

• Engine type: FA

  Courtesy of SUBARU OF AMERICA, INC.

• Engine type: EJ

  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 B2789 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 (GROUND SHORT CIRCUIT). 
   1. Disconnect the keyless access control module connector.
   2. Using a tester, measure the resistance between the keyless access control module connector and chassis ground.

      Connector & terminal 

      (B574) No. 20 - Chassis ground:

      Is the resistance 10 kΩ or more?

      Yes:  Go to  3.

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

3. CHECK HARNESS (OPEN CIRCUIT). 
   1. Disconnect the ID code box connector.
   2. Using a tester, measure the resistance between the keyless access control module connector and the ID code box connector.

      Connector & terminal 

      (B574) No. 20 - (B422) No. 2:

      Is the resistance less than 1 Ω?

      Yes:  Go to  4.

      No:  Repair or replace the open circuit of harness.

4. CHECK HARNESS (OPEN CIRCUIT). 

   Using a tester, measure the resistance between ID code box connector and chassis ground.

   Connector & terminal 

   (B422) No. 5 - Chassis ground:

   Is the resistance less than 1 Ω?

   Yes:  Go to  5.

   No:  Repair or replace the open circuit of harness.

5. CHECK HARNESS. 

   Using a tester, measure the voltage between ID code box connector and chassis ground.

   Connector & terminal 

   (B422) No. 1 (+) - Chassis ground (-):

   Is the voltage 11 - 14 V?

   Yes:  Go to  6.

   No:  Repair or replace the faulty portion of the power supply circuit.

6. CHECK ID CODE BOX. 
   1. Turn the ignition switch to ON.
   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 B2789 displayed? (Current malfunction)

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

   No:  Go to  7.

7. CHECK ID CODE BOX. 
   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:  Replace the keyless access control module. Refer to SECURITY AND LOCKS>KEYLESS ACCESS 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.