Horn Operation
WARNING: This page is about a different car, the 2018 Ford Focus. However, it is still accessible from the selected car via links, so may be relevant.
The horn switch uses sets of contacts separated by springs. One set is connected to ground and the other set is connected to the horn signal circuit. When the driver airbag is pressed, it pushes down on the upper set of contacts, collapsing the springs and allowing the contacts to touch. When the contacts touch, it completes the circuit and provides the ground signal, which is routed through the clockspring to the BCM. The BCM grounds the horn relay coil to energize the relay. When energized, the horn relay provides voltage to the horns, enabling the horns to sound.