Fuel Level Sensor: Description and Operation

Fuel Pump Module (Typical):

FUEL LEVEL SENSOR
The fuel gauge level sending unit is attached to the side of fuel pump module. The level sensor is a variable resistor.

Its resistance changes with the amount of fuel in the tank. The float arm attached to the sensor moves as the fuel level changes.

The fuel level input is used as an input for OBD II. If the fuel level is below 15 % of total tank capacity several monitors are disabled. There are diagnostics for the level circuit open and shorted.