Principles of Operation
WARNING: This page is about a different car, the 2008 Mercury Mariner and 2008 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
The smart junction box (SJB) is also known as the generic electronic module (GEM).
The SJB supplies the control voltage to the horn relay (part of the SJB). When the horn switch (part of the steering wheel) is pressed, ground is supplied to the horn relay sending voltage to the horn, enabling the horn to sound.
The SJB provides a momentary on then off ground when the panic button is pressed on the integrated keyhead transmitter (IKT).