Principles of Operation
WARNING: This page is about a different car, the 2005 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
The horn switch is integral to the driver air bag module. When the horn switch is pressed, ground is supplied through the clockspring to the powertrain control module (PCM). The horn relay is then energized, supplying voltage to the horn, enabling the horn to sound. The horn relay is integral to the central junction box (CJB).