Theory of Operation

WARNING: This page is about a different car, the 2011 RAM Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

The Fuel Level Sensor is attached to the side of the Fuel Pump Module. The sending unit consists of a float, an arm and a variable resistor track (card). The fuel transfer pump is also attached to the Fuel Pump Module. A constant 5-Volt signal is supplied to the resistor track of the fuel gauge sending unit. The resistor track is a variable resistor used to vary the voltage signal depending on fuel tank float position. As fuel level increases, the float and arm move up, which decreases voltage. As fuel level decreases, the float and arm move down which increases voltage. When the fuel tank level is measured below 15%, the following fuel system monitors are shut off: P0191 (Fuel Pressure Idle Diagnostic portion of it), and DTCs P0300, P0301, P0302, P0303, P0304, P0305, P0306. The TIPM will illuminate the MIL lamp immediately after this diagnostic runs and fails. The TIPM will turn off the MIL lamp after the diagnostic runs and passes in four consecutive drive cycles.