2001 Ford Expedition Q&A
2001 Ford Expedition Question: My 2001 expedition just failed the emissions test why with codes p0442,171,174?
you need a shop with a scan tool, smoke machine to find the failure in the evap system. as far as the 171,174, it could be several things but once again you need a shop to check it for you and give you a bid. common issues are pcv valve, vacuum leaks, low fuel pressure and mass air flow failure. Roy - mastertech6371