Check Power Supply And Ground Circuit Of Backup Unit

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.

1. Disconnect the backup unit connector.
2. Measure the voltage between backup unit connector and chassis ground.

Connector and 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.

Measure the resistance between backup unit connector and chassis ground.

Connector and 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.