I have this same code on my 03 navigator, and it was a small rubber hose elbow that needs to be replaced. Its $13 dollars, and the part number is YS4Z-6A614-BA. I do not know exactly where it is on the expedition, but I think its a PCV valve line where it connects to the rear of the intake manifold. Just reach around the back of the engine. It should look like an elbow hose
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.