OK, so I received the p0401 code, so in my research the DPFE sensor came up alot. I decided to change it myself to save a buck. The truck has 140k+ miles on it and it may have been the original sensor. I will say it took alot of effort to remove the sensor and in doing so I broke the stem off that attaches to the sensor and it was inside the tubing. I then pulled the tubing off the two metal tubes that attached to a larger tube. I was able to remove the broken piece from the tubing and cleaned the inside of the tubing. Which, by the way, was orange in color. So here is the problem. Before assembling everything back I noticed the metal tube, one of the two that lead up from the engine where the rubber tubing sits was clogged with orange stuff. I took a paper clip and poked the clog and it mostly fell back down the metal tube which connects to the larger tube. My question now is, how screwed am I? I put everything back together and drove down the block but noticed nothing. Will this debris just blow back up and malfunction my sensor or is this going to lead to a more expensive repair?

Thanks to all who might reply,
Mike

Oh, the truck is a 2001

 

I don't know what your outcome will be but here is what your working with.
The metal tube has a 040" orfice between the small pipes.
The DPFE measures the pressure difference accross the orfice and sends the result to the computer.
The 401 code is lack of or low flow on a test the computer requests at startup and once during each drive cycle.
The forign material you poked back in may not cause a problem but time will tell.
The blockage likely is in the intake manifold behind the EGR valve.
All you need to do to check this is apply vacuum to the EGR valve just enough to open it.
If the port is open, the motor will stumble and run rough while idling as the indication it's open.
If this check failed, you would have not needed to replae the DPFE but there is always a chance the DPFE needed replacement from accumulations you found.
This system has to work with contaminated exhaust at all times.
Good luck.

 

Here's an illustration of the basic EGR valve test mentioned above:

Engine must be fulled warmed up & idling when this test is done.

 

I have an F150 of the same year & engine as you. Changing my DPFE was the easiest thing I've had to do on the engine except for maybe adding windshield washer. Most of the effort was in researching where it was & finding a Youtube video of how to change it.
Check this diagram:

There are many others like it on the internet.
The pipe going from the number 3 to the exhaust pipe is called the "orifice tube assembly" -- tech writers had to call it something.
Its path is nearly vertical from where it connects at its top end, to the EGR valve, to a point below its two offshoot metal tubes that are connected by your thick orange rubber hoses to your DPFE. Below that point it bends to the rear & somewhere down there connects to the exhaust system.
See labeled photo below of my EGR valve, orifice tube assembly and DPFE attached to the assembly's 2 branches by the orange (black with dirt) rubber tubes you mentioned.
<iframe title ="Preview" scrolling="no" marginheight="0" marginwidth="0" frameborder="0" width="640px" height="480px" style="padding:0;background-color:#fcfcfc;" src="https://skydrive.live.com/embed?cid=E6418942DC619CB4&resid=E6418942DC619CB4% 213687&authkey=AC1mhqhcD9q0ibY"></iframe>
Click on this photo to get a higher resolution image.
The EGR valve, DPFE and the orifice tube assembly are marked.
The red oval with a white center marks an apparent seam in the tube assembly which is where (IMHO) the orifice diaphragm exists -- in any case, it has be to located between the two metal branches that connect to the DPFE for the system to work as diagrammed.
When the EGR system is actually recirculating exhaust gas, the flow of the exhaust gas is UPWARD to the EGR valve & then into the intake manifold. This would tend to blow small bits of debris away from the orifice.
On the other hand, if you had knocked a huge piece of debris or a gooey bunch of sludge into either or both of the metal branches of the assembly just below the DPFE, you might have clogged one or both branches.
2nd simple test of EGR system (Credit to Bluegrass7, who mentioned it to me elsewhere);
Engine at hot idle.
Disconnect both legs of the DPFE -- they should now slide very easily off the rubber hoses if you have just installed them.
Feel whether or not there are pulsations of exhaust gas coming up the metal assembly branches towards where the DPFE used to connect. If so, both branches are at least partly open, as is the orifice hidden within the assembly. Total lack of exhaust gas flow in either branch means its clogged (assuming your engine is running.)
I suppose a partial clogging of the orifice tube assembly could cause an emission code error, but it seems unlikely.
I recently serviced this system, and sprayed some carb cleaner down the orifice tube at its upper end, since this part has to be disconnected in order to change out the EGR valve. That is a bit harder to do that change the DPFE.

 

Wow, great photos and thank you for your response. In the photo you posted the blockage was in the left tube, or the one closest to the fire wall. So it may blow back up the tube to the sensor or possibly block the diaphragm/ restriction in the egr tube. I'm going to replace the egr valve at some point just as a general maintenance and to experience changing it. I've noticed a drop in gas mileage, which could be many things I assume, and I'm sure just popping a new one on can't hurt. Again, thank you so much for your reply!

Oh, I went the wrong direction...so the blockage was maybe sent to the egr and beyond?

 

Now remember, any material in the orifice assembly has to move uphill to block anything. I don't think that's very likely. Do the two tests Bluegrass 7 and I have recommended. If you have actual exhaust gas flow through all the tubes we've mentioned, and actual exhaust gas recirculation (the vacuum pump test), you are highly unlikely to have any blockage in the orifice assembly or the EGR valve.
There is another issue - partial blockage in the passages from the EGR valve to the intact manifold, the infamous P0401 codes. There have been many, many posts on this issue on this forum, do a Google search for them.
Part of removing the EGR to replace it, is disconnecting the orifice restrictor assembly at its topmost point. The junction cannot be seen in my photo. Then you can run a vacuum cleaner hose (would have to be a very narrow one) right down the assembly to suck out as much loose crud as you can, and you can even spray carb cleaner right down the assembly toward the orifice, to loosen up gunk then suck it out with a vacuum cleaner. As I understand it, cleaning the orifice itself is nearly impossible if sticky material gets wedged in it -the orifice is very small.
There is an adapter between the EGR valve and the intake manifold which can be partly removed. The adapter has a hollow passage which directs EGR flow into the intake manifold. The adapter has 3 bolts, only two of which can be removed easily after the EGR comes off. Even fastened by a bolt, the adapter can be cleaned out through and through, be do that if you change the EGR valve.
I don't see the point in changing a functioning EGR valve assuming you have no error codes and the engine passes the 2 tests we've mentioned. However, last week I did replace my EGR valve, which I discovered was utterly clogged to the point the valve was frozen shut. Here is a video of how the valve should operate on my new EGR valve:
Operation of EGR Valve for 2001 F150 4.2L, off the engine - YouTube
The EGR adapter connects to a horizontal passage at the top front of the intake manifold which runs to the back of the manifold, and branches off to each cylinder's intake where there are special EGR ports installed. These tend to clog up in old 4.2L V6's and require a lot of work to access and clean. When some of these ports are blocked and some are open, the diagnosis of the error codes can become really difficult.

 

Wow, ARTFD, great info. I have been trying to diagnose my 2006 F-150 4.2 and think there might be an issue with my DPFE, but on mine it is a self-contained module. I couldn't really get to the little hose between the solenoid and the valve to do the test, but I have two small plastic tubes running to the sensor, one orange and one red. While the truck is idling, i am getting full manifold vacuum from each. To my mind, this means that the valve must be open at idle, and that the tube to the exhaust manifold might be clogged as well. There is not much info out there that I could find about these self-contained DPFEs, so I thought I would see if I'm approaching this correctly....
Thanks,
Louie

 

Good Thread!

 

Thanks artfd for that nice diagram. As a novice mechanic diagrams and such are truly a great help to further my uderstanding of the different car systems