Code P401

P0401 indicates poor exhaust gas recirculation (EGR) flow. The valve itself may or may not be sticking or clogged with carbon, but at the same time, more likely the EGR passages under the intake manifold are clogged. But aside from all that - one of the more common causes of a P0401 code for this vehicle historically (depending on your engine) is a faulty "DPFE sensor". This stands for differential pressure feedback EGR sensor. When this sensor fails, the system doesn't work properly. Hands on testing is required before making guesses at repairs. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops