Temperature Gauge
WARNING: This page is about a different car, 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.
On early production diesel engine vehicles, the instrument cluster is hardwired to the engine coolant temperature (ECT) sensor. When the engine temperature is low, the resistance of the water temperature indicator sender unit is high, thus restricting the flow of current to the instrument cluster. As the temperature of the coolant increases, the resistance decreases, allowing more current to flow to the instrument cluster. On vehicles equipped with gasoline engines and all late build vehicles, the instrument cluster receives the temperature signal from the powertrain control module (PCM) via the standard corporate (SCP) network.