System Operation
WARNING: This page is about a different car, the 2013 Ford F-550 Super Duty, 2013 Ford F-450 Super Duty, 2013 Ford F-350 Super Duty, and 2013 Ford F-250 Super Duty. 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.