So, First found this Thread about a Year ago when I started getting the P0449 Code on my 2000 Chevy Silverado Z71 1500. I never got around to replacing the Solenoid, as, I am not comfortable removing the Bed, or Dropping the Fuel Tank. Just thought I would "live with it".
Well...I had a "Stuck" Fuel Filter & had bought some FREE ALL penetrating oil to free up the frozen nuts on the Fuel Line.
While waiting, for no apparent reason, I decided to spray the hell out of the Purge Solenoid area because I hated the fact that I KNEW what was wrong, I could SEE the Part, but I couldn't access it.
Guess What? After over a Year of the SES Light being on because of the P0449 / P0440 Codes, the Light went off! It has now STAYED off for over 2 weeks (came back on the other day when it was raining, but went back off again).
Could it be that the Penetrating Oil actually penetrated the housing & Freed the Stuck Solenoid?
I don't have the answer, but I haven't replaced the part, and I'm no longer getting the code.
I have 360+ Thousand Miles on this Baby and it runs like a CHAMP!