2007 GMC Sierra

Engine Performance problem
2007 GMC Sierra V8 Two Wheel Drive Automatic 77000 miles

My check engine light came on a few weeks ago and it would not come on some times until I drove for awhile. Now it stays on all the time. I had the code read and it came out p0449. How do I go about trouble shooting what the problem is. It happened right after I changer the spark plugs, wires, and the battery so I might have knocked something loose but I cant seem to find anything. Any help would be great.
July 1, 2010.

Hello and thanks for donating

DTC P0449 : Evaporative Emission (EVAP) Vent Solenoid Control Circuit

This code is common to appear if the battery was disconnected for any reason. I suggest erasing this code from the system and waiting to see if it comes back. If it does come back then the EVAP vent solenoid valve may be faulty.

How do I erase the warning code. I disconnected the battery but that did not do it. Also how difficult is it to change the evap vent solenoid never done one of those.

Jul 2, 2010.
You will need to use a diagnostic scan tool (or have local auto part store do it) to erase the codes stored. The solenoid should be mounted on the back side of the tank. From under the truck you can remove the valve wiring connector, remove the valve from the tank and remove the lines from the valve and canister. If there is no hose on the new valve, then use 5/8 heater hose to run the filter for the valve beside the transmission.