I have a 2010 Navigator, 50,000 miles, 5.4L engine and Im getting a CEL and code P0446. I checked my gas flap, I dont have a gas cap, and it appears to be closing properly. I filled the tank up and drove around 200 miles and the light did not go out. If my problem is not with the gas flap most people talk about the purge solenoid. My question how do test this solenoid other than spending $120 and doing a switch and see.