That 401 code is EGR valve. There's a metal tube that runs off the EGR valve to exhaust manifold, this tube gets clogged with carbon deposits and eventually the flow of exhaust gasses gets blocked. Remove EGR valve and the metal tube and use brake cleaner and a pipe cleaner or something to clean gunk from tube. Just replacing EGR valve won't clean that tube out.
Trying checking your fuel injector, it might be faulty. The Emissions or EGR system could also be the culprit in this case. You can also hook up and OBDII scanner and reset it or just disconnect your negative post battery cable for 5 minutes and insert it back on.