Glow Plug System
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2003 Ford Pickup, 2003 Ford F550 Super Duty, 2003 Ford F450 Super Duty, 2003 Ford Excursion, and 2003 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The glow plug system is mounted directly into the cylinder heads, controlled by the Engine Control Module (ECM) and designed to preheat the cylinders for faster cold weather starts and smoke reduction.