I'm getting two error codes; P0401 and P0171. How can they be corrected?
on 2004 Ford Escape

I'm thinking there is a single problem causing the two codes

Asked by for the 2004 Ford Escape
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.