I have 2005 GMC Envoy. I noticed the gas

The float is in the gas tank. Difficult fix. Probably have to replace it.

GMC sent me a letter saying that gas guage not working has been a problem and they will fix and pay half.
Also my mechanic says that it is common to get a check engine lite when you add gas to tank, especially when you fill it. Sometimes I will take off gas cap and let air out then replace cap and the check engine lite will go off. (usually). Nothing to worry about.

Common problem is for the tiny stepper motor to go out in the back of the guage. Can buy off of E-bay, very cheap.

Check the fuses first, possible the sending unit on the fuel tank is bad.

The problem is probably the fuel level sensor in the fuel tank.It can be replaced separately.You don`t have to replace the fuel pump and the level sensor.Hope this helps.Good luck.

It is most likely your fuel level sending unit has gone bad. It sits inside your fuel tank to tell the fuel guage how much gas you have in the tank.

The sending unit for the gas gauge is in the fuel tank and part of the fuel pump module, it is not sold seperately. Price is around $350.00, 2 hours labor to install the part.

it sounds like the fuel level sensor in the gas tank is bad,causing a misreading and fluctuation,,replace it and that should help,,

The oxygen sensor has nothing to do with the fuel gauge. There are two possibilities for the gas gauge error, first it could be the in-tank gas level sensor or it could be a defective stepper motor which drives the gauge. A professional scan tool can determine the fuel level being sent by the in-tank sensor, if that disagrees with the gauge, then the stepper motor needs replacing.

The sending unit in your tank is bad replace it.

most likely a fuel sending unit problem in the tank. could also be problem in dash but sending unit is first suspect