DPFE bad?
 

Hey guys I'm dealing with a 401 code on my 2000 6cyl. Been running it with the vaccuum line to the EGR blocked since I last tried to fix it at which point I replaced the EGR, the DPFE(NAPA part/Echlin), and the regulator solenoid. Replacing the three components didnt solve my problem which led me to block the EGR hose and I've been running it like that for the past couple years. Anyways, I've cleaned and verified my EGR valve is functioning by hooking an active vaccuum line to it which made it run poorly as it should have. My signal wire at the DPFE is reading 0.021-0.028 V at idle. I do not have a vaccuum pump to test whether the signal fluctuates like it should but from the voltage numbers I've found(0.9V), my reading is far below. Can I infer the DPFE is bad based solely on the signal measurement at idle being out of spec?

Correction: Signal voltage at idle should be 0.21-0.28V (typo)

Just got the codes read and it shows:

P0401-EGR flow insufficient
P0301-Cylinder 1 Misfire
P0174-System too lean

Your DPFE is bad. They dont fail outright, sometimes its just a gradual failure. But it sounds like yours is nose diving.