Principals of Operation
WARNING: This page is about a different car, the 2007 Ford Pickup, 2007 Ford F550 Super Duty, 2007 Ford F450 Super Duty, and 2007 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The starting system is electronically controlled by powertrain control module (PCM). The PCM recognizes the signal from the ignition switch and provides a ground for the starter relay. The energized relay provides voltage to the starter solenoid, thereby allowing the starter motor to activate.