Automatic Transaxle
WARNING: This page is about a different car, the 2010 Mercury Mariner and 2010 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
The PCM monitors gear status information. When the transaxle is in REVERSE (R), the PCM provides a ground for the reversing lamps relay coil. When the relay is energized, voltage is supplied to the reversing lamps.