I have run my 2005 crd with the orm mod for three years now. For ny state inspection I have to connect to the computer. In the past i would reconnect the maf sensor and the light would go out. This year in stayed on showing PO401. I have a snapon modis scanner and have cleared the code several times and keeps comming back. I have a friend that does inspections and we have tried to coax it pass inspection, it passes emissions but then losses comunication just before it issues the sticker. When i clear the code the crd reddiness monitors set instantly but the inspection computer must be looking for more information. I have had the egr out and inspected it. It works freely as well as the fcv and the spool moves back and forth freely. My question, is there a flow chart on the operation of the egr, voltages, ohms, frequency etc,? I have search the form for hours and can only find that they are replaced or cleaned. No flow chart on how to diagnose the code PO401 other than its probably the egr or fcv or maf. I am hoping to find the problem, rather than throw expensive parts at it. Any help would be greatly appreciated, thanks in advance!

if the EGR is ok and move freely a P0401 can be a clogged intake or MAP , try to clean the MAP , I can help you for diagnosis the electronic EGR due for the different system , but this code mean less gas , and if always seem ok , I'll try to clean the MAP sensor first , after the MAF and if the problem persist try to clean the intake manifold

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I will check the map next. I did have it out and clean it this spring, (I unententionally put a mix of dirty wvo/diesel in the jeep last fall and it gummed up every thing to the point it would not start. I had to take apart each injector boil the parts in clean diesel then scrape the crud off each component, drop the tank scrub it, clean the crd rail and injector lines, the filter head was coated, I even had to clean the fuel supply line. The only component I did not take apart was the high pressure pump although I did run 200 degree diesel fuel thru the system for the first half hour.) How does the ecu sense low flow egr? is there a sensor on the pintle or just through map sensor or both. My egr spool was spring loaded to shut and Im guessing the step motor opens it. I will check All-Data tomorrow to see if they show anything. The intake had plenty of crud but not as bad as many I seen here. Also I have been planning to make a ccv vent similar to what has been used some farm tractors years ago, tap into the exhaust after the muffler (no back pressure) at a 45 degree angle with 1/2 tubing inserted into the pipe about 1 inch and have the venturri effect suck the mist into the exhaust. I should be hot enough to partially burn it so not to have a back window full of oily mist