Passive Anti-Theft System (PATS) - With Intelligent Access (IA): Overview
WARNING: This page is about a different car, the 2013 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
PATS protects the vehicle from theft by preventing the ignition from turning on or the engine from starting unless a programmed Intelligent Access (IA) key is detected inside the vehicle. PATS cannot disable an already running engine.