Hey sorry if this has already been posted and answered I'm a newbie. i have an 06 Silverado with the 5.3. my ses light came on, pulled the code and it was p0455. i thought it was the gas cap since it was a locking aftermarket one. replaced with the stock gm cap cleared the code and it came back on. after taking it the dealership they smoke tested it and said that my "vent valve soleniod" was bad and needed to be replaced. That bill would cost me $300 when all said and done. I'm not gonna pay that and have automative knowledge. Since then i have cleared the code and now it comes up with the p0455 (evap emissions leak detected large) and p0449 (evap emissions vent valve/solenoid malfuntion). I think i know where it is located at but not exactly sure so any help? Also i have read that a cheaper part (a few have said one from a cavalier) would work. Any ideas? Also any valid part numbers? Many thanks in advance for the help.