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

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. Roy