The sending unit is located at the top right rear corner of your car's gas tank. You can get it inside by removing the fuel pump access cover on your trunk floor and then disconnecting the electrical connector from it. The fuel gauge sending unit, also known as the fuel level sensor or fuel sender, is an electronic device that measures the amount of gasoline in the gas tank. The fuel level sensor consists of two parts, one is mechanical float, and the other side is a variable resistor. (1) The fuel level sensor basically works like a potentiometer. The float arm is connected to a variable resistor. As the float rises and falls with the fluctuation of gasoline level, it moves back and forth across the resistor to increase or decrease the resistance value. The signal voltage changes with respect to the change in resistance value.