Either the fuel gauge itself is messed up, or your sending unit is messed up. The best way is to have someone with diagnostic equipment "monitor" the data from the fuel tank. That'* English for, dealer puts the Tech 2 on it to watch the data.
The Following User Says Thank You to Mike For This Useful Post:
Thanks for the suggestions! Luckily it was a simple fix. The needle had spun all of the way around to the wrong side of the pin. I searched around the internet and found a fix for the gauge. I was amazed to find that a magnet can spin the needle around to the proper spot. I purchased some strong magnets and it worked!
Apparently it can also be caused by a low battery, or on some gm vehicles, for no obvious reason at all. . . In my case there was no change to the car overnight but, just to be safe, I am going to check the battery condition and the connections today.