Check Power Supply And Ground Circuit Of Backup Unit

Wiring diagram: 

DC power supply circuit Ref. to WIRING SYSTEM>POWER SUPPLY CIRCUIT>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK FUSE  .
   1. Turn the ignition switch to OFF.
   2. Check the fuse on the upstream of the backup unit. Ref. to SECURITY AND LOCKS>RELAY AND FUSE>INSPECTION .

   Is the check result OK?

   Yes:  Go to  2.

   No:  Replace the defective fuse.

2. CHECK POWER SUPPLY  .
   1. Disconnect the backup unit connector.
   2. Turn the ignition switch to ON.
   3. Measure the voltage between backup unit connector and chassis ground.

      Connector & terminal 

      (i112) No. 3 (+) - Chassis ground (-):

      (i112) No. 5 (+) - Chassis ground (-):

      (i112) No. 8 (+) - Chassis ground (-):

   Is the voltage 9 V or more?

   Yes:  Go to  3.

   No:  Check the harness for open or short circuit between the backup unit and the fuse.

3. CHECK GROUND CIRCUIT  .

   Measure the resistance between backup unit connector and chassis ground.

   Connector & terminal 

   (i112) No. 6 - Chassis ground:

   Is the resistance less than 10 Ω?

   Yes:  The power supply and ground circuit are OK.

   No:  Repair or replace the harness.