DTC B2793: Backup Power

DTC detecting condition: 

When +B power supply (SUB) input is less than 9.5 V continuously for 10 seconds with ignition switch ON. (Voltage check is executed every one second)

Trouble symptom: 

• Entry cannot be made.
• Power supply control cannot be executed.

Wiring diagram: 

Keyless access with push button start system Ref. to WIRING SYSTEM (IMPREZA MODEL)>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (HEV))>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. 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]. 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.

2. 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. Start the engine, and let it idle for 40 seconds or more.
   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 B2793 displayed? (Current malfunction)

   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.
3. CHECK FUSE  .
   1. Turn the ignition switch to OFF.
   2. Check the fuse. Ref. to SECURITY AND LOCKS>RELAY AND FUSE>INSPECTION .

   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.

4. CHECK HARNESS  .
   1. Disconnect the keyless access Control Module connector.
   2. Using a tester, measure the voltage between the keyless access Control Module connector and chassis ground.

      Connector & terminal 

      (i75) 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 .

   No  : Repair or replace the open circuit of harness.