I have read through the posts and found alot of good information. My truck continues to get the PO 401 code after replacing the DFPE sensor about 6 months ago and the EGR valve yesterday. I keep getting extensions from the Maryland VEIP but I don't think they will give me anymore. What else should I try? All the DFPE wiring and harness coneections are tight, the EGR is fresh and the vaccum line is new. What else could it be? Thank you!

 

You might want to try asking this in the V6 section, seeing as they specialize in the 4.2 department.

 

check for plugged egr ports. what brand dpfe did you get? suck test the egr. it should cause the engine to stall or almost stall. if it does nothing then its either plugged ports or a bad egr diaphram(or your not doing it right). i know the egr is new but that means nothing if it was an aftermarket egr.