Two problems related to fuel delivery have been reported for the 2006 GMC Envoy. The most recently reported issues are listed below.
Fuel level sensor (2006 GMC Envoy XLT) it was floating back and forth at first then it rests on "e" and the light stays on and the alarm keeps ringing that my fuel level is low. It has left me stranded more than once. I have contacted gm and was told that they have had several vehicles come in with the same problem. Now it doesn't float at all it just stays on "e" and the light and bells are on.
While driving, check engine light came on. Fuel tank gauge started to continually shift from whatever state the fuel tank was in to empty then after some time revert back to normal fuel capacity at the time. Contacted onstar for a diagnostic and they stated there is a problem with the fuel sending unit.