My fuel gage is being very erratic. on 2002 Buick Rendezvous

Says it's full, when I know it's not. Another time says it's empty, when I know it's not. It's usually saying one or the other. I keep track of my fuel by the mileage,trip meter. What could be the problem?

Asked by for the 2002 Buick Rendezvous
either the fuel sender unit is bad or the connector under the back door on the drivers side. it is common for this connector to rot out over time.

Is this connector by the l.r door inside or under the vehicle?
1 more answer
I had the same problem. they had to change the whole front dash panel of gauges. about $300 or so to do it.I think it was the computor system. had dealer repair.