How much gas in the tank when this happens? Does it only happen with less than, say, 1/4 tank? Does it ever happen with a full tank? Does the light then go off soon there after? The light is driven by the same sensor that operates the fuel gauge (as far as I know, anyway - the tank has a fuel level sensor and a pressure sensor - the latter is for the emissions test that is performed every so often).

I can't imagine why the light would come on with more than 1/8 of a tank.