For 1990-2009 cars

When the ignition switch is either in the ON or the START position, voltage applies through the TURN fuse to one of the following components:

• | The backup lamp switch for manual transmission.

• | The transmission range switch for automatic transmission.

When the shifter is in the R position, the switch closes. The voltage applies to the backup lamps in the tail lamps. Since the tail lamps are ground permanently at G400, the lamps will light.