The gas gage on our 2001 Nissan Aultima stays on ful all the time how can i fix this problem at home

There is a small resister unit in the gas tank,on your fuel pump, that registers fuel level by electrical current. If this is stuck in the up position it will register full all the time.Don"t laugh, but find a rough road and see if it will come loose,No I'm not kidding.If this doesn,t work the unit will have to be replaced because its broken. This involves changing a perfectly good fuel pump out as well to fix this because the two components are built together. Good Luck