oldchev
Full Access Member
I had the P0455 on my 04 Yukon Denali. I found the vent valve solenoid was sticking due to dirt. I took it out and using a 12v source activated and deactivated while blowing air though both ends of it. Lots of dirt and grit. Once clean and working good I checked it with air going through and deactivating etc. Put it back on and it cleared the code in two or three starts. It did it again later so I just replaced it. Then again maybe 6 months later only this time the purge valve on top of intake manifold quit. I used the same process but this time I just think the solenoid was no good. It only clicked once and a while. Replaced and haven't had a problem since and that about 4 years now.
