Fuel Gauge not working on 2005 GMC Envoy

Gas tank is full but gauge stays on empty. Light comes on and then off, then back on. Only way to gauge gas is to use fuel used indicator (from steering wheel). What repair will be needed and approximately what will the repair cost be? Thanks.

Asked by for the 2005 GMC Envoy
I sounds like there is a problem with the fuel level sensor inside the fuel tank. If that is indeed the fault there should be a fault code stored in the Powertrain Control Module. The cost to replace the sensor should be $335 - $407.
how can I change the sensor
You must remove the fuel tank to replace the fuel level sensor for your Envoy.