Theory Of Operation
WARNING: This page is about a different car, the 2011 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
The Full Open Switch indicates when the gate is a few degrees from full open position. The switch is closed when the liftgate is fully open and the switch is open when the liftgate is either fully closed and latched or between full open and closed. It can be checked by manually opening and closing the liftgate while monitoring the scan tool.