The signal from the Pontiac Fuel Sending Unit is translated from an electrical impulse to a visual reference for the driver to interpret by the fuel gauge on the dash board.
The function of the fuel sending unit is to register the fuel level in the tank and take this physical property and convert it to an electrical impulse. At the receiving end of the electrical impulse is the fuel gauge on the dash that takes the impulse and coverts it back to a physical representation so the level indicator in the gauge can be representative of the fuel that remains in the gas tank on your Pontiac.
The fuel sending unit in your Pontiac has a sensor that is attached to the float in the fuel tank. As the level rises and falls, the sensor makes a reading and sends the appropriate signal to the gauge on the dashboard. If the float has a leak in it and does not remain on top of the fuel, a false reading will be taken. Another way the Pontiac fuel sending unit might be giving a false reading is when there is a short in the sensor. In both instances the fuel tank will have to be lowered and a new fuel sending unit will have to be put into place.
There is a rare occasion when the wiring leading from the fuel sending unit to the gauge on the dashboard is disconnected or broken on your Pontiac. Instead of a false reading there will be no signal and the gauge will showing that there is no fuel in the tank. This is when the short or break in the wire has to be tracked down and replaced before the correct signal can be transmitted for the driver to use.