Check Power Supply And Ground Circuit Of Backup Unit

CHECK FUSE AND RELAY .
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.
CHECK POWER SUPPLY .
1. Disconnect the backup unit connector.
2. Measure the voltage between backup unit connector and chassis ground.
  Connector and terminal
  
  (i313) No. 3 (+) - Chassis ground (-):
  
  (i313) No. 5 (+) - Chassis ground (-):
  
  (i313) 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.
CHECK GROUND CIRCUIT .
Measure the resistance between backup unit connector and chassis ground.

Connector and terminal

(i313) 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.