For all of you following my build thread, you know that I am not a bodyman. I am a mechanic, and recently had trouble with my truck. I'm going to walk through the diagnosis and show a tip that can save a part and some $$. Hopefully I can help you with this the way you all have helped me learn bodywork.
So here is the Amber light on the dash that I hate when it shows up.
And here is the code with the scanner.
This is a pretty common problem with the purge vent valves, and is the same for the trucks, tahoes, suburbans, and their gmc equivalents. The valve is located in front of the gas tank by the charcoal canister on trucks, and behind the bumper on suv's.
Grab some jumpers and connect to 12v source. The valve should click and you can physically see it move. Mine did not.
There are reasons they fail, but without getting long winded one of the reasons is that ethanol attacks the seals which causes them to get dry and stiff causing the valve to stick. Grab some silicon spray lube and spray in the large port.
Try your 12v source agin. It may take some tapping and multiple hits with voltage to get it free. Make it open a few times moving the silicon lube good.
This doesn't work every time, but these things are $40 - $80 depending on where you get them. It easy to do so well worth an attempt before just shelling out for a new one.
Hope this helps someone out!