i worked on a chev 2008 6.6 durmax for code p0401 unit had several codes history p2463 p0401 p1448 p244b p0234 p244c p2563 p0101 i cleared codes p2463 and p0401 came back within 2 miles checked code p2463 for d p h soot level it explained if code p0401 was pre... Login to read more.