At a loss at this point. I have a 1997 Pontiac Grand Prix that the fuel gauge always reads past full. I've tried replacing the instument cluster with now change, i tried replacing the sending unit with no change. I'm at a loss. Anyone on here familiar with this issue? TIA Pete

The gauge works on resistance. O - 88 ohms. If you lose conection from the sender to the cluster then your gauge will peg because it is seeing infinite resistance. (much more than 88 ohms) Sounds like you have a problem between the sender and the gauge or a bad ground. Check your ground path. There should be one from the engine to the body, one at the sender and one for the instrument cluster however this will be in the connector for it. You can buy a 50 ohm resistor at radio shack to help trouble shoot the wiring. If you get a good connection with it the gauges should show half full. Then you can check your way thru the harness till you see gauge go full then you know where you lost the signal. Hopefully its just a ground thing. Bill

Pete, Always check the gauge fuse first. If that checks out, Bill has you going in the right direction. It should be an open in the sender wire between the cluster and the tank unit(fixed many with same symptoms in past). Steve

Fuse is good. Hunting for the problem is going to be "fun". I hate electrical stuff. Pete

Disconnect the sender wiring at the tank and check the harness side wire for resistance. I'm not sure on the newer cars, but the older cars, the needle would peg if the wire was shorted to ground, not open. I've always used that info to troubleshoot a gauge, just ground the harness wire, and if the gauge pegs out, it's a bad sender or sender ground.