2008 Ford Expedition Eddie Bauer. Keep getting code P0446. Replaced 2 wire w/connector under car as was bared and somewhat broken. Cleared light & code. A week later light came back on. p0446 again.

This time since I couldn't get the part right away my message center displayed my gas cap. I checked the cap with the emissions machine and it was fine. My part, the evaporative valve which is located on the driver side firewall, came in and I replaced it. Cleared the code and went about my normal driving. 2 days later the light is back on and I'm again at p0446. I'm at wits end. Any suggestions?