Code P0401

As some may know I have a surge in my engine (only felt in overdrive under 2000rpm) that I have been trying to figure out for some time.

I thought it was the spark plugs so I replaced them today with a set of NGK V-power plugs gapped to .054, when changing the plugs on the V6 Sohc the front driver side plug is hard to get to from underneath, as the EGR tube is in the way, so I went at it from the top, but had to bang my rachet against the EGR tube when tighting and loosing the plug due to clearance issues.

After the plug install the vehicle ran really good, but the surge was still there maybe a bit worse and about 3 minutes after driving the vehicle the "check engine light pops on". I check the code with my trusty Xcal II and it tells me that it is code P0401 the EGR system. The light did not come on with the previous surging I had been experiencing before the plug swap.

The EGR valve was replace about two years ago with a NAPA one, the Vacuum motor and DPFE are both less than a year old and purchased from Ford.

Anyone have any thoughts as to what this could be? Does the EGR Tube ever need to be replaced?

I have 175k mi on this vehicle and I drive it hard.

Worst part is I replaced my year old Brisk Racing $12/ea spark plugs with Cheapo NGK's and they were perfectly good.

Anyone?


With a code P0401 where should I start?? The EGR valve, DPFE sensor and Vac controller are all about a year old. Never checked the pipe.

What do you clean out the EGR tube with?

Any help is greatly appreciated.

I would start with checking the vacuum lines for clogs and definantly check for clogs in the EGR tubes from the exhaust, use some brake cleen and compressed air to clean it.

Thanks.

I hear that the EGR tube cracks on explorers commonly, has anyone else heard this?

It can crack, but you would hear it.

Thanks Cobra, I will start by cleaning it.

Well I replaced the lower EGR tube with a brand new one and after about 20 miles the code came back...

I am thinking now that it is the DPFE sensor, though I did replace this about two years ago.

Funny thing though after I drive the car, I get out and can smell exhaust fumes coming from under the hood, wonder if this could be a clue to where the problem is?

Any thoughts or suggestions?

Is the EGR tube installed correctly? Any leaks? Sounds?

A code P0401 most likely means one or more of the following has happened:

• The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
• There is a blockage in the EGR (tube), most likely carbon buildup
• The EGR valve is faulty
• The EGR valve may not be opening due to a lack of vaccuum

Possible Solutions

In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.
• Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticable difference in RPM's with the EGR open
• Clean out the EGR valve and/or tubing to remove deposits
• Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model)
• Replace the DPFE sensor (with a good quality / OEM one)
• Replace the EGR valve

Thanks Al.

By the process of elimination all that is left is the DPFE sensor.

I installed a brand new EGR tube, Cleaned and tested the EGR valve and cannot hear any leaks.

I bought the DPFE that is installed now 2yrs ago and it is bad already what a waste of $68