Originally Posted by BillBoost37
99% it would be a bad sender. That other 1% is bad wiring or ground. My bet would be a bad sender.
This is Marty talking now.
If I remember correctly in the late 90'* GM was having probs with the metal they were using for the float rod in the tank, and the chemicals in the fuel were corroding the rod, thus not allowing it to swing up/down with the fuel level.
GM supposedly corrected this sometime during 99 (my old 99 was starting to do this slightly when I sold it).