2003 GMC Sonoma Owner's Manual - Page 167

Here are four things that some owners ask about. None of these show a problem with your fuel gage: At the gas station, the gas pump shuts off before the gage reads full. It takes a little more or less fuel to fill up than the gage indicated. For example, the gage may have indicated the tank was half full, but it actually took a little more or less than half the tank's capacity to fill the tank. The gage moves a little when you turn a corner or speed up. The gage doesn't go back to empty when you turn off the ignition. Low Fuel Warning Light This light comes on briefly when you start your engine. This light comes on when the fuel tank is low on fuel. To turn if off, add fuel to the fuel tank. See Filling Your Tank on page 5-7. 3-40