I have a 2008 envoy and the engine light came on.

you must have overfilled the gas tank at one point recently...and flooded the carbon canister...The First click....NO MORE temptation to put another tiny bit in there...perhaps to round up to the nearest dollar...but no you can't do that no more! drive a couple of half-tankfulls and it will clear~

put the factory cap back on...it will offer the correct amount of vacuum/pressure~

I still have the factory gas cap on the rig. Ill try the running half tanks and see if that works. Could there be other issues?

the 02 sensor is a common problem...other things would make it run crappy such as an ambient air temperature sensor, a throttle postition sensor, a coolant temp sensor...these things make the ECU happy when they are functioning normally, if they are not the ECU will not provide a correct air/fuel mix, but overfilling the tank is something that even I ....just can't stop at one click....ooooh~

No reason to guess at what it is. Get the codes read at the parts store. Write down the trouble code number and post it here. Someone will advise the most cost effective solution.

turned out to be my alternator. Thanks for your help!

my code is P0411

had my 08 envoy parked for almost 2 month till I got the funds to do an oil change cause I was over like almost 1000 miles my recommended change and I finally deciced to get an oil change and on my way there the motor light turned of any suggestions what it can be TIA