Looked all through the threads trying to find something on this code with no luck. So I am having EGR excessive flow problems I replaced the EGR Valve cause it was sticking. That was more than 2,000 miles ago. Still getting the code so looked up in haynes one of the things they say to check is 30 to 70 ohms on the EGR vacuum regulator well had way less assumed it was shorted. Checked the new EGR vacuum regulator and has way less ohms also. I put the vacuum gauge on the regulator w/ eng. running w/ a 7 volt signal going into the reg. and the vac gauge didn't move even with the truck in drive.

Any ideas of what I should do? I hate driving w/ the CEL on.

 

I'll assume that this is an F150 that you're talking about. I drive the same truck for work,and it's got the same problem.I believe we've tracked it down to the EEC being bad-the voltage feed for the DPFE and EGR solenoid is supplied from the EEC,and if it's too high or low-then it needs replaced. The EEC is looking for a predetermined value for voltage at a particular EGR flow-if it's out of that range,it'll set a code and turn on the SES light. It's over at the shop now having the EEC replaced,and as soon as it gets back I'll let you know if that fixed the problem. The EEC catch code on the work truck is WIZ2-there may be an issue with this particular EEC if you've got the same one.
JL

 

Well,I just spoke with the shop,and that's not the problem. Changed the EEC,and it's still got the same P0401 code.So far we've replaced the EEC,DPFE,EGR,EVR solenoid and nothing's changed.
JL

 

I also have changed the EVR, and EGR. Yes it is an F150 meant to specify that. Light came back after I replaced the EVR. Figure I will wait to finish figuring it out till after I get my new headers and exhaust which might create more of a headache. Just a thought the EGR tube leaking at the header fitting would that possibly be part of the problem?