po449 EVAP emmission valve/solenoid-code advance auto

I have Diagnosed this code few times on GM cars and trucks. Code P0449 indicates that there is a problem with your Evaporative Vent Valve Solenoid. On your truck it is on the right hand side of the fuel tank. A fuel cap alone will NOT repair this code. I would get a new fuel cap as well, though because I find that the GM Fuel Caps go in about 2-3 years. I do Emissions work in California. You can go to a GM dealership and ask for the Evaporative Vent Valve Solenoid Assembly and a Fuel Cap. Only use factory parts for this repair.

Code P0449 on your 2006 GMC Yukon is related to the EVAP solenoid operation, Replacing the gas cap probably won't be of much help. There is a factory service bulletin that may help - the number is #02-06-04-037H. This may involve installing a new canister vent solenoid and filter kit.