Normal Operation
WARNING: This page is about a different car, the 2005 Lincoln LS. However, it is still accessible from the selected car via links, so may be relevant.
The driver door arm/disarm switch grounds either circuit 31S-AA78 or 31S-AA79 to the driver door module (DDM). The DDM then communicates over the standard corporate protocol (SCP) communication network to the front electronic module (FEM) to arm/disarm the alarm system.