my check engine light come on with a P0401 OBD-II Trouble Code of Insufficient EGR Flow. I have replace both the egr valve and the DPFE (differential pressure feedback EGR) sensor, with no luck. It sometimes goes off and then come back on. I was just wondering how else I could go about fixing this. THanks once again guys, any help is greatly appreciated
the truck is a 1998 Ranger 3.0 XLT

i had the same problem about 3 months ago. an O2 sensor in the 2nd cat was going off, said the mix was too lean. i bought the sensor from FORD for about $140. and spent a week trying to get the old sensor to come off (couldnt geta good angle) and a few days later, the light went off and hasnt come back on since. the NEW sensor is still sitting in my glove box. so i have no idea what the problem was. as for replacing the sensors, and still having a problem, i'm told it could be a NUMBER of different things!!!

Ummm, O2 has NOTHING to do with his EGR problem, Tim.

Jared, the hoses to the DPFE can crack / deteriorate. Take a good look at them.

There is also an EGR Vacuum Regulator Solenoid near the back of the engine. I THINK if THAT were bad, you'd have additional codes.

You can also remove the EGR valve and clean it and its tubes. You'll find a lot of carbon, which could also be the problem.

99% of the time, insufficient flow is the DPFE, so I suspect a hose problem to it.

Im going to check all of my hoses and replace them when I get my avm hubs. I should be getting them tomarrow!!

prob your dpfe sensor.... change your egr valve and dpfe at the same time though brecasue a bad dgr valve can fowl your dpfe

did you not read he replaced them both already.

Im guessing carbon buildup in the tube.

Here's a couple of very good resources regarding Ford DPFE/EGR System Operation & Testing:

http://www.tomco-inc.com/Tech_Tips/ttt35.pdf

http://www.tomco-inc.com/Tech_Tips/ttt36.pdf

See generally: Ford DPFE/EGR System Summary

Nice.

Way to bring the facts, Joe.

Good post.

thanks so much, I am going to check everything now

change the egr hoses (that run from the DPFE to the exhaust manifold), this fixed my problem.

Changed out the DPFE, went to autozone and asked if I could replace my DPFE for a different one and they had a metal case one. I replaced the dpfe hoses to and cleaned out the egr tube. THe CEL has been off for two days so far and usually it comes back on the same day. SO I think I may be in the clear. Im just crossing my fingeres, thanks for all the great help I could have done it without this forum

I had the same thing on my 99 3.0L . After replacing EGR, O2 sensors and chasing the same codes down, I replaced the Idle Air Control unit. It took care of the problem and was very easy to replace.
O2 sensor in front was a pain to get out. Had to put the socket on from below and use a long pipe on the ratchet handle from the top of the engine compartment to get a good angle on it. It came right out that way.