Key-In-Ignition Warning Chime
WARNING: This page is about a different car, the 2006 Mercury Montego, 2006 Ford Freestyle, and 2006 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.
When the key-in-ignition switch closes, it sends a voltage signal to the instrument cluster, which then sounds a warning chime, provided the ignition switch is in the OFF position and the driver door is open. The instrument cluster sounds a steady tone, which continues until the key is removed, the ignition switch is rotated to the RUN position, or the driver door is closed.