I have an 04 Bonneville that has just over 42,000 miles. Had a problem this afternoon when I got in and went to leave work. The fuel guage was acting erratic. ( going from full tank to 1/4 tank.) Then, as I would go down the road, the fuel hand would go up and then come back down to 1/4 tank. I know the tank is full of gas, (filled it up on Saturday)Has anyone else had this problem. Also at the same time the A/C quit working. I shut the car off and then restared the car with the same problems. Went on down the road a few more miles and then everything was back to normal. Any info would be greatly appreciated.

Check this post. Different problem but the fix will help you in your case.

http://www.bonnevilleclub.com/forum/...ic.php?t=81387

Thanks for the info.
I will check it out and let you know.

Tried the grounding lug to no avail. Everything looked to be in great shape.
I took the lug off and cleaned around it and put it back together. Still have the same problem. Dealer says to bring it in and let them check it out. Might have to break down and do just that.

My guess is that the two issues are probably not related.

My fuel gauge did this and I fixed it using this:

http://www.bonnevilleclub.com/forum/...ic.php?t=71718

and this is my post after I fixed it (it has part number and price):

http://www.bonnevilleclub.com/forum/...hlight=#901862

It may be a bad sending unit, but since you have a GXP it is more likely a bad stepper motor in the gauge cluster. Others have had the same issue. I have 3 of my gauges acting crazy over the past 50-60k miles - my coolant temp gauge is useless (sometimes it points straight down), the volt gauge will occasionally read max or '0', and the fuel gauge freaks out likes yours did at least once a month so I have to rely on the fuel readouts in the DIC.

Well, I have an appointment tomorrow to see what Pontiac says the problem is. Can't wait for the results of that. I am sure they are going to tell me a line of you know what. I will keep you posted.

Took my GXP to the dealer'* last Friday (Sept. 14th) for them to fix the gage and other problems.They replace the fuel pump and sending unit. Picked it up Tuesday night and still had the same problems. Left it there and they finally found the problem, so they said. They are now replacing the entire instrument cluster. Takes about 2-3 days. They also replaced the key fobs. Stated this is what was going wrong with the electrical. (don't really know how, but I have two new key fobs) They gave me a Cobalt LS to drive for my inconvience.

Has anyone else had any problems like this on their GXP'*? Mine only has 42,700 miles on it. I change the oil every 3,00 miles and every 3rd oil change I replace the fuel filter. I hope this isn't foreshodowing problems to come.

Thank you for all of the advice and help.

Well,
After 11 days and $1,000 later, I got my Bonnieville back from the shop with everything working this time. They replaced the fuel pump, connector o-rings, key fobs, and the entire instrument cluster. I'm so glad I got the extended warranty with this car. Just had a $50.00 deductible. The instrument cluster was $611.00 by itself. I thought this was a bit pricey. Anyway, my fuel gage problem is fixed and I am back on the road again.

WOW !!
I have the same problem,, o well, looks like I will have to pay up