So last december this code popped up on my 2004 gmc sierra. turned out the EVAP vent solenoid was bad and it was replaced under my trucks warranty. My truck is out of warranty now and the same code popped back about a month ago. I called the dealership where i got it fixed and the solenoid was 1 year warranty so i brought it to the dealership for them to test it. They say the check engine light just turned off when i dropped it off (i think they cleared it and couldn't get the code to pop back up and didnt know what else to do) but they said they tested the solenoid and it was fine. so anyway i took it home and about a week later the code came back on.

i did a search a found this:

So could my problem be the vent is clogged? The EVAP solenoid is brand new and supposedly working fine. It said the problem is caused by dust getting in there. Sense i got it fixed last december the truck hasnt seem any dirt roads or dust. All highway driving. Could the heavy usage of salt they use up here clog up the vent?