you replied my ? was answered I don't see the answer

Erratic fuel gauge in not uncommon on some newer cars. You may wish to try the following on your 2003 Buick Le Sabre; Add a bottle of Chevron Techron Concentrate Plus every couple of months. It has an additive that is supposed to help clean the fuel gauge sending unit. Here is some more information: http://bit.ly/Techron_Concentrate_Plus. If this does not work replacement of the fuel level sensor or repair of the dash fuel gauge may be necessary.

It sounds as though the wires have been reversed to the gauge or the sending unit - UNLESS someone tried to 'jump' the car when the battery was unable to start the car. Then the polarity of some gauges can be reversed. For some problems, we have to bite the bullet and take it to a service department, either dealer or independent.