So a while ago my truck started throwing a P0456 and P0442. Yesterday I had my friend diagnose it with his smoke machine and we located the leak in what his professional manual called the "vent control valve". All of the research I've done says that the vent control valve is the one that mounts directly to the side of the canister, but that's not the part that's leaking. The part that's leaking is located on the passenger side rear, above the frame rail. It's got two small rubber lines attaching it to a small white piece and a green electrical connector that plugs into it from above. Here's the pictures I managed to get of it: The white piece It's connected to: So, what is it called? It's obviously a valve of some sort, given the electrical connector and the way it's connected to the rest of the system, but after doing some reading I don't believe it to be the vent control valve.