Principles of Operation
WARNING: This page is about a different car, the 2010 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
The horn system is designed to sound the horn when the horn switch is pressed. The horn relay is supplied voltage at all times through the battery junction box (BJB). Pressing the steering wheel pad horn switch provides a ground circuit to the control side of the horn relay. In turn, the switch side of the horn relay is closed, allowing voltage to be applied to the horn.
The control side of the horn relay is also controlled by the lighting control module (LCM) during the anti-theft perimeter alarm operation. The LCM grounds the control side of the horn relay on then off, causing the horn to sound. For the anti-theft perimeter alarm, refer to ANTI-THEFT - PERIMETER article.