Fuel 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.
The instrument cluster is hardwired to the fuel sending unit, which is a variable resistor controlled by the action of a float arm. When the fuel level is low, resistance in the unit is low. When the fuel level is high, the resistance is high. The instrument cluster micro-processor monitors the input from the fuel sender and commands the fuel gauge indication according to the fuel level data.