DTC B2784: Antenna Circuit (Push Engine Switch)

WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.

DTC detecting condition:

When the keyless access control module received erroneous data for the antenna coil from the transponder key amplifier through the transponder communication (communication between keyless access control module - push button ignition switch) upon the transponder collation start operation.

Trouble symptom:

Power cannot be switched, engine does not start even when the access key is pointed toward the vehicle.

Wiring diagram:

Keyless access with push button start system Ref. to WIRING SYSTEM>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

For replacement procedure of keyless access control module, refer to the "REGISTRATION MANUAL FOR IMMOBILIZER" provided as a separate volume.
Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to KEYLESS ACCESS WITH PUSH BUTTON START (DIAGNOSTICS)>GENERAL DESCRIPTION>CAUTION

CHECK HARNESS (OPEN CIRCUIT) .
1. Disconnect the connector from the push button ignition switch.
2. Disconnect the connector from the keyless access control module.
3. Using a tester, measure the resistance between the push button ignition switch connector and the keyless access control module connector.
  Connector & terminal
  
  (i135) No. 9 - (i92) No. 19:
  
  (i135) No. 10 - (i92) No. 22:
  
  (i135) No. 14 - (i92) No. 21:
  
  (i135) No. 8 - (i92) No. 24:
Is the resistance less than 1 Ω?

Yes : Go to 2.

No : Repair or replace the open circuit of harness.
CHECK HARNESS (GROUND SHORT CIRCUIT) .
Using a tester, measure the resistance between the push button ignition switch connector and chassis ground.

Connector & terminal

(i135) No. 14 - Chassis ground:

(i135) No. 9 - Chassis ground:

(i135) No. 10 - Chassis ground:

Is the resistance 10 kΩ or more?

Yes : Go to 3.

No : Repair or replace the short circuit of the harness.
CHECK PUSH BUTTON IGNITION SWITCH .
1. Replace the push button ignition switch. Ref. to SECURITY AND LOCKS>PUSH BUTTON IGNITION SWITCH>REMOVAL
2. Connect the disconnected connectors.
3. Turn the ignition switch to ON.
4. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start (Collation)]. Ref. to COMMON (DIAGNOSTICS)>CLEAR MEMORY
5. Read the DTC of [Keyless Access with Push Button Start (Collation)] using the Subaru Select Monitor. Ref. to KEYLESS ACCESS WITH PUSH BUTTON START (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)
Is DTC B2784 displayed? (Current code)

Yes : Replace the keyless access control module. Ref. to SECURITY AND LOCKS>KEYLESS ACCESS CONTROL MODULE>REMOVAL

No : Malfunction occurred in the push button ignition switch.