I'm thinking there is a single problem causing the two codes
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2004 Ford Escape Question: I'm getting two error codes; P0401 and P0171. How can they be corrected?
Answer #1mastertech6371 September 24, 2011, 21:54Master
nope, 2 separate issues.
401 is an egr flow code. need to get a diag on the components for the egr system. the most common failure is the dpfe sensor but you need to have it verified first.
the 171 is a lean code. it could be a vacuum leak, mass air flow failure. pcv problem or low fuel pressure. it also needs to be diaged properly to verify.