Ignition Key Lock Solenoid
WARNING: This page is about a different car, the 2006 Mercury Milan and 2006 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
The solenoid is incorporated in the ignition lock. In manual selector lever position P the ground connection to the solenoid is cut. The locking pin does not engage in the ignition lock.
In all the other manual selector lever positions, the ground connection to the solenoid is closed and the locking pin engages in the ignition lock.
When the manual selector lever is not in position P, removal of the ignition key is prevented.