DTC B2789: Id Code Box Communication

DTC detecting condition: 

• When communication between keyless access CONTROL MODULE and ID code box is interrupted for a set amount of time.
• Open or short circuit in the wiring harness between keyless access CONTROL MODULE and ID code box

Trouble symptom: 

Engine will not start.

Wiring diagram: 

Push button start system Ref. 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. Using the Subaru Select Monitor, clear the memory. Ref. to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>Clear Memory Mode 
   2. Read the DTC using Subaru Select Monitor. Ref. to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) 

   Is DTC B2789 displayed?

   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.
   4. Using the tester, measure the resistance between terminals.

      Connector & terminal 

      (B574) No. 17 - (B422) No. 2:

   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 and chassis ground.

   Connector & terminal 

   (B574) No. 17 - 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 (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. Using the Subaru Select Monitor, clear the memory. Ref. to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>Clear Memory Mode 
   2. Read the DTC using Subaru Select Monitor. Ref. to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) 

   Is DTC B2785 displayed?

   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. Turn the ignition switch to ON.
   2. Using the Subaru Select Monitor, clear the memory. Ref. to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>Clear Memory Mode 
   3. Read the DTC using Subaru Select Monitor. Ref. to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) 

   Is DTC B2789 displayed?

   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.