System Operation
WARNING: This page is about a different car, the 2012 Ford Pickup, 2012 Ford F550 Super Duty, 2012 Ford F450 Super Duty, and 2012 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The glow plug system is electronically controlled by the GPCM. If the coolant temperature is below 60°C (140°F), the GPCM energizes the glow plugs immediately after the key is placed in the ON position. Then, depending on the readings from the Engine Coolant Temperature (ECT) sensor, as well as the battery voltage, the GPCM determines how long the glow plugs are energized. The on time of the glow plugs is independent of the WAIT-TO-START lamp on time.