DTC B2793: Backup Power

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 +B power supply (SUB) input is less than 8.5 V continuously for 10 seconds with ignition switch ON. (Voltage check is executed every one second)

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 DATA MONITOR .
1. Turn the ignition switch to ON.
2. Using the Subaru Select Monitor, check the following items in the [Data Monitor] of [Keyless Access with Push Button Start (Power Supply)]. Ref. to KEYLESS ACCESS WITH PUSH BUTTON START (DIAGNOSTICS)>DATA MONITOR
  - Control Module Voltage (Backup)
Is [ON] displayed?

Yes : Go to 2.

No : Go to 3.
CHECK DTC .
1. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start (Power Supply)]. Ref. to COMMON (DIAGNOSTICS)>CLEAR MEMORY
2. Start the engine, and let it idle for 40 seconds or more.
3. Read the DTC of [Keyless Access with Push Button Start (Power Supply)] using the Subaru Select Monitor. Ref. to KEYLESS ACCESS WITH PUSH BUTTON START (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)
Is DTC B2793 displayed? (Current code)

Yes : Go to 3.

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 FUSE .
1. Turn the ignition switch to OFF.
2. Check the fuse. Ref. to WIRING SYSTEM>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM
Is the check result OK?

Yes : Go to 4.

No : Replace the fuse. When the replaced fuse is blown immediately, check the power supply circuit for short-circuited.
CHECK HARNESS .
1. Disconnect the connector from the keyless access control module.
2. Using a tester, measure the voltage between the keyless access control module connector and chassis ground.
  Connector & terminal
  
  (i91) No. 1 (+) - Chassis ground (-):
Is the voltage 9.5 - 16 V?

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

No : Repair or replace the open circuit of harness.