Horn Operation
WARNING: This page is about a different car, the 2018 Lincoln Navigator. However, it is still accessible from the selected car via links, so may be relevant.
The BCM monitors the ON/OFF state of the horn switch using a circuit that passes through the clockspring and SCCM.
The horn switch uses sets of contacts separated by springs. The lower set is connected to ground and the upper 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 a ground signal through the clockspring and SCCM to the BCM horn input. The BCM then grounds the horn relay coil to energize the relay. When energized, the horn relay provides voltage to the horns, enabling the horns to sound.