2004 Chevy Trailblazer Code P0496

That is the evap purge canister. Try tightening your gas cap 3 clicks after tight and clear the code and that should help. If you don't tighten the gas cap it sets a code.

Sometimes the cannister purge sticks and if you give it a light smack with a screwdriver handle it let's it close an dwork properly. The valve is inside the frame about the middle of the truck by the gas tank. Actaully have a pro look at it though as if it has to be changed, he'll know how much it costs.