2001 f150 supercrew 4.6 liter. code p401 insufficient egr flow keep showing up .i replaced the egr valve, the pdfe sensor, and the egr vaccum selinoid, took off the throttle body and totlly cleaned it out (it looks brand new all holes are cleaned), changed all vaccum hoses, the egr tube that goes to the exhaust is new. and the darn code still keeps coming up. any suggestions!!!

 

Did you use aftermarket parts or genuine OE parts?

 

Im thinking Autozone DPFE sensor.........

 

Apply vacuum to the EGR valve while its running to make sure everything works. The engine should stall if everything is good. If it stalls, get a Ford DPFE.

 

I don't know if this will help but here goes. I had the same code. Checked
the egr and everything worked fine. Then I remembered removing a vacuum line on the back of the intake so that I could replace the IAC valve. I checked that hose and noticed that the clamp was partially on and partially off. I corrected that and really didn't think anything more about it. ( Didn't really think that small a thing could cause a problem)
I kept driving the truck because it was running fine. Was going to wait until I had time to replace the DPFE sensor before clearing the code. After
the perverbial 100 miles the cel went out and hasn't come back. What I'm
trying to get at is , any small vacuum leak in that system can cause the code.