DTC B2793: Backup Power

DTC detecting condition: 

When +B power supply (SUB) input of less than 9.5 V continued for 10 seconds, when the ignition switch is turned ON. (Voltage is checked at one second intervals)

Trouble symptom: 

None

Wiring diagram: 

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

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DATA MONITOR. 

   Using the Subaru Select Monitor, check the following items on «Data monitor» of «Keyless Access with Push Button Start». Refer to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>DATA MONITOR .

   • «ECM power supply voltage (back-up)»

   Is «ON» displayed?

   Yes:  Go to  2.

   No:  Go to  3.

2. 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. Start the engine, and let it idle for 40 seconds or more.
   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 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. 

   Check the fuse. Refer 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 

      (B573) No. 1 (+) - Chassis ground (-):

      Is the voltage 9.5 - 16 V?

      Yes:  Replace the keyless access control module. Refer to SECURITY AND LOCKS>KEYLESS ACCESS control module .

      No:  Repair or replace the open circuit of harness.