Normal Operation
WARNING: This page is about a different car, the 2005 Mercury Montego, 2005 Ford Freestyle, and 2005 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.
The parking aid system is enabled when the ignition switch is in the RUN position and the transmission is in REVERSE. When the parking aid system is enabled, the audio system volume is cutback, allowing the 750 Hz variable warning tone that is generated from a parking aid speaker to be clearly heard.