Car makers recycle exhaust gas back into the engine to reduce combustion temperatures and pollutants. However, in order to make the engine run smoothly, car makers have to carefully meter the recirculated exhaust, injecting it into the intake manifold only under the proper conditions. To do that, they have developed exhaust gas recirculation (EGR) valves and sensors to detect how well the EGR valve is working. The sensing portion of the system is important because the exhaust contains soot, and that soot can clog up the metering portion of the EGR valve.
The Ford EGR system uses 3 components:
• an EGR valve that opens and closes a passage from the exhaust to the intake ma
nifold,
• an Electronic Vacuum Regulator (EVR) that opens and closes a passages from the intake manifold to the diaphragm of the EGR valve, and
• a Delta Pressure Feedback EGR (DPFE) that measures the change in exhaust pressure before and after a restriction in the exhaust tube that leads up to the EGR valve.
Here’s how it works
When certain driving conditions are met and the computer wants exhaust gas recirculation, it provides a pulsing voltage to the electronic vacuum regulator (EVR). The EVR is a solenoid valve. When it opens, it allows intake manifold vacuum from port 5 to flow into port 6 on the top side of the EGR valve. The vacuum pulls up on the diaphragm, lifting the pintle off the pintle seat. With the pintle off its seat, exhaust pressure forces exhaustgas up through the EGR tube, the EGR valve, and into the intake manifold at port 4. On the way up to the EGR valve, the exhaust gas passes through a restriction. The DPFE sensor hoses are connected to ports 1 and 2—before and after the restriction. By comparing and reporting the differences in pressure, the computer can determine exactly how much exhaust gas is flowing through the EGR valve.
What goes wrong
Exhaust gas contains water vapor. Ford did consider the ramifications of this water vapor getting into the DPFE and forming ice. So they programmed the computer to ignore an EGR malfunction if the temperature is below 32°F. Unfortunately, Ford didn’t give enough consideration to the impact of corrosion inside the DPFE, and that’s what causes most of the EGR related problems.
Do it yourselfers and professional technicans make an all-too-common mistake if they automatically replace the EGR valve when they see an EGR related code. In fact, the valve itself is usually the most reliable component in the system.
How to troubleshoot
Step 1) Check the condition of the vacuum hoses going to the DPFE sensor and the EVR. Look for cracks or tears. Replace the hose if you find any.
Step 2) Check the operation of the DPFE with the engine off, key in the run position. Using a digital voltmeter, check for voltage on the brown/light green wire. Look for a reading between .45 and 1.1 volts. If your reading is outside that range, you have one more voltage check to perform before replacing the sensor. Check the voltage on the brown/white wire. It should read 5 volts. If it doesn’t, the sensor isn’t getting power from the computer. Then it’s a whole new ballgame. If you have 5 volts, and the reading from the brown/light green wire is outside the range, replace the DPFE. After replacement, perform the voltage check again to eliminate the possibility that the EGR valve is not seating properly.
Step 3) Leave your meter connected and start the engine. The voltage SHOULD NOT CHANGE! That’s because there should be no EGR flow at idle. If the DPFE voltage changes, either the EGR pintle isn’t seating properly and it’s allowing exhaust flow past the seat, or the DPFE is bad.
Step 4) Remove the EGR valve and check the condition of the pintle, pintle seat, and the EGR passages. They will be coated with black soot. But the passages should not be clogged and the pintle should move off its seat with the application of vacuum. Clean the pintle, pintle seat, and passages with carb or throttle body cleaner.
©, 2007 Rick Muscoplat
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Car makers recycle exhaust gas back into the engine to reduce combustion temperatures and pollutants. However, in order to make the engine run smoothly, car makers have to carefully meter the recirculated exhaust, injecting it into the intake manifold only under the proper conditions. To do that, they have developed exhaust gas recirculation (EGR) valves and sensors to detect how well the EGR valve is working. The sensing portion of the system is important because the exhaust contains soot, and that soot can clog up the metering portion of the EGR valve. 
nifold,
44 comments:
thx for the article. mine is doing something i cant seem to find anywhere.
it set code po401 one day last week. i bought a reader to see what it was. insufficient egr flow detected. i erased the code to see if it would come back.
sure enough the next day it came back with code po402.
each day it seems to set the opposite code. too little then too much the next day.
sorry if this isnt the place to do this
erratic flow usually points to a sticking EGR valve. Remove yours and spray it down with carb cleaner to remove the carbon. Then use a hand vacuum pump to make sure the diaphram opens and closes the pintle smoothly. If not, replace the entire valve.
Hi Rick, I really appreciate your column. Question, can a DPFE sensor function intermittently? In other words, could it function for a while (days or even minutes) and then start to fail, and the work again?
Thanks,
Mike
You bet!. Especially in cold weather the sensor can be intermittent. When the engine shuts down condensation can form and freeze inside the sensor. The computer has a software telling it to ignore the readings from the DPFE in extremely cold weather until the engine warms up and the computer is convinced that the ice has melted. But, all that condensation causes corrosion on the electrical contacts and that gives you intermittent operation.
Best to replace it.
Hi:
My hoses are splitting, and I am wondering where I can get replacement hose. Can I just go to any autoparts store, or do I have to get a specific hose from a ford dealer?
Thanks,
BWP
I did the voltage checks that you suggested. The voltage at the brown/green wire was .94 but when I bring up the engine RPM it only goes up to .97 volts. Shouldn't there be a significant change in voltage at higher RPMs if the EGR and DPFE are functioning properly?
The computer has to see "closed loop" conditions before it will allow EGR flow. That means engine running for 3 minutes and up to operating temps. If you raised RPM on a cold engine, the computer won't allow EGR.
I have a 3.0 ltr. ford ranger which is throwing the same code p0401 consistently I even changed the egr valve. Now I am getting what seems to be an engine miss or chug at low speeds. The chug is all the time now. I have also performed a complete tuneup on this motor. What is my challenge here?
Hi Rick, Thank you for the super helpful information. This might sound stupid, but I will ask anyways. So there are 3 wires coming from the plug that goes to DPFE, I think I will be able to figure out the colors no problem, but the question is out to measure the voltage on the wire as of course there is no exposed part on the wire so as to put the digital voltmeter. Sorry like I said it might be a stupid question but hopefully you can give me a simple tip on how to do this.
It's not a stupid question. But it does tell me that you haven't taken the time to read ALL 150 articles on my blog.
Seriously, pop this link into your browser and it explains everything on how to pierce a wire.
http://free-auto-repair-advice.blogspot.com/search/label/Ferret
What would cause a 327 code? It has something to do with EGR low voltage. I've been trying to get this fixed forever... Help
WOW!!! Excellent explanation!!!
Thanks soooo much for taking the
time to put this together.
Also this website is killer.
Again, thanks a lot for your time
and sharing your knowledge
John T. Blair WA4OHZ
www.team.net/www/morgan
Hello: I am experiencing simmilar problems. code 0401 on a 98 sable with the durotec 24 valve engine. Found and replaced sensor and valve and hoses leading to and from exhaust (changing to the new plastic sensor means you need longer ref hose) Also took out valve, it was caked with carbon, so i replaced it as well for good measure. Sensor i bought from autozone was malfunctioning, throwing a p1401 code, replaced it, and with high hopes started driving to the epa station. p0401 popped up again. I have checked all hoses (blew through them, and none seem to be leaking. I must pass an emissions test in the next 2 weeks. The only thing left on the list from a p0401 code is the egr solenoid (i belive that is the same vacum as what this article states is the evr?) Am I missing something here? From everythign i have read from ford technicians, it is very, extremely unlikely that the vacum is baed. Is there any way i can test the vacum? Again, hoses are good, sensor and valve are new, but i am still registering insufficient flow detected. WHAT CAN I DO????? Please advise, i really need help with this one. I love my car, and frankly, won't be able to afford another until the housing marked improves and i can sell off one of my flipped homes. Thank you for all of the info posted above.....Sincerely, Mike B, a concerned sable owner and impromptu mechanic.
Did you read this blog article about cleaning the throttle body?
http://free-auto-repair-advice.blogspot.com/2007/08/ford-egr-codes-p0401-p1408fix-clogged.html
Read my other P0401 post regarding cleaning the throttle body.
Hi Rick, thanks for the article. I have a 99 explorer 4.0 L and I just replaced my DPFE sensor and hoses. The car was fluttering and making a annoying noise during acceleration. Now the noise is gone but the fluttering continues. It is the worst around 1700 RPM. Do you have any suggestions?
Hey Rick –
I’ve got the same error code, and really appreciate the advice. Our repair facility seems to be giving us information that doesn’t account for everything and they seem to be falling into the misdiagnosis issues you relate to above. So thanks for giving us great resources on this topic.
I do want to follow up, though, on the posting from anonymous. We got our car back with the check engine light on and were told that a sensor might have been bad. I don’t think that’s it, and I think we’ve got a problem in the EGR system, too. We have been encouraged to get a complete tuneup and are getting the engine miss or chug at lower speeds as well. What should we do?
Thanks again for a great topic and a great site.
Hi Rick
I have been reading some of the posts trying to find a solution. I have an 01 Taurus with the 3.0 ohv, I'm getting the P-0401. I put a new dpfe in, and a new vaccum soleniod, took the egr off and made sure it was opening and closing properly and cleaned it up, took the thottle body off and made sure the passages were clear (it has the molded plastic intake plenum and it is a straight shot from the egr in to the intake, there are no small holes to get clogged, it is also sealed with an o-ring not a gasket the o-ring was ok), and I checked the egr tube and hoses to make sure they were clear. Everything checked out, But I too am getting the chug almost like a small missfire while driving. Usually when I am just lightly feathering the accelerator or coasting, it is more pronounced when the ac is on. I changed the plugs and wires about 15k mile ago. Still the only code I am getting is the egr flow insufficient. Do you think I got a bad dpfe? and do you think the chuging and the egr code can be related? The last question would be would the idle air control cause the chuging if it was bad or not operating properly?
Rick,
I had my DPFE replaced earlier this year at a shop and then, yesterday, it melted. I replaced it last night, easy enough, and my CEL went off today. However, the mechanics (at several places) are blindly saying that my cat is clogged and recommending replacement. I've asked about hoses, etc and they all say the "safe bet" is to replace the cat and everything will be fine.
My 97 Explorer is my baby and, while she is running just fine today, I don't want any really bad problems from something I didn't fix when I replaced the DPFE.
Should I go with the theory of replacing the cat?
Thank you!!
Tina
Can anyone tell me when Ford changed the DPFE sensor? The one on my 2001 Taurus doesn't look anything like the one in the picture or in my Hayne's manual. Instead of a 3x2 block, it's really small with the two vacuum lines plugged into the bottom of it. Also, my EVR solenoid reads about 32.5 OHMS...haynes manual says should read 20. Is it bad? Codes I keep getting are 0401 and 1401. Please help. Thanks
Hello: I recently had a 0401 and 1401 problem with my 98 sable. If you have teh duratec doc v6, there is no manual that will have pictures of your egr system whatsoever (unless you special order it). Disconect your battery to clear the trouble codes out. then here's what you need to do:
1)remove your throttle body, and dispose of the old gasket.
2)Reach behind your air intake manifold to find the egr sensor (aka the dpfe) you need a deep socket 10mm wrench to do it right. take it out (go ahead and cut the hoses, it's easier to jus replace them...any autoparts store will sell you lengths of it, make sure you get a couple inches more than it looks like you need, just be sure you marked which ports of the exauhst tube on the other side of the hoses get either the thick or the thin hose)
3)put in your new dpfe and hoses
4)look at the manifold where the throttle body mounts on it. There is a port there that is c-shaped. you may not even recognize it it will be so coated in black gunk. It will be in the bottom left (7 o'clock) of the throttle body mounting area. clean it out, using a hard metal wire and some throttle body cleaner (while you have it out you may as well clean the throttle body as well). Be careful, though, those parts are aluminum and it is very easy to scratch them. make sure that throught the top of the port air will be able to flow unimpeded to the EGR valve (it's like a 90 degree turn inside that port towards the egr valve). Air needs to be able to travel through that c-shaped area all the way to those 3 square shaped outles that go back into the air intake manifold. Clean the whole thing until it looks sparkly new ;) one more thing to be wary of: see the valve on top of the manifold? that's the idle air control valve that allows air to bypass the throttle body when your car is at idle. don't get any throttle body cleaner in there, because it can ruin some of the parts.
5) once all your stuff is clean, reattatch your throttle body with a NEW GASKET (can't sress this enough), clean air hose, and lastly batery cable (if you took off your egr valve, make sure it's back on too). Start your car...it wiull idle very very hot while the alcohol in the throttle body cleaner burns out. Drive it to reset your idl;e perameters like it says to in your owners manual. If the light comes back on the NEXT time you drive your car, than it is either your pcm, EGR solenoid, or the egr valve itself. However, it is very unlikely that this is the case. If you cleaned the c-shaped port and replaced your dpfe...most likely the problem is solved, and your gas mileage will improve exponentially t' boot.
Happy times, drive safe.
Mike
help please, i have an 87 ford ranger, about 45 secs after start up idle drops way down and runs rough. black smoke out exhaust. weather driving or idleing. about 45 secs to 90 secs later idle picks up smoke goes away. i have paid over 800.00 having mech do intake cleanning replace plugs dist wires coil etc now they want to charge 300 to replace egr. i did see them clean it it was real bad, they had to force the shaft in using table. please help thanks joe
First off, the shop should have checked the EGR valve before they did an intake manifold cleaning, plugs, wires, etc. EGR is a known cause of poor idle.
Second, if the valve was bad enough that they had to force the shaft, the valve is toast.
My advice? Find a new shop. These guys are just throwing parts at the problem. They do not know how to diagnose the problem.
Replace the valve yourself. The valve is around $115 at www.rockauto.com.
How do you remove a egr valve from egr tube if rusted. I've tried Blaster, Liquid Wrench, heat and a combination.
I am trying to replace an egr back pressure sensor on my 2001 Ford Taurus but am having trouble locating it in the car. do you have a diagram available? Thank You Stacey
Stacey:
Most likelyt it is bolted to the back oof your engine, on the drivers side, behind the air intake manifold. Look at where your air filter is, and follow the big black hose up to the throttle body, which is mounted onto the AI manifold. If you remove the clean air hose and the throtte body, most likey you'll see it back there. It doesn't look the same as the new ones at autozone, it is metal, not plastic. Remove your throttle body, buy a new gasket, and read this intire post-thread on how to clean that c-shaped port that is a part of the AI manifold where the throtte body connects. I bet that is the cause of all your problems, but replace the dpfe sensor as planned for good measure anyways. You'll need to buy new hoses for it. good luck and drive safe.
-mike b. sable owner and impromptu mechanic. Hope rick doesn't mind my contributions.
This is a great how-to/instructional! Greatly appreciate it.
I checked my DPFE lines: brown/white gives 5 volts run or idle, like you said. Brown/green gives 2.03 volts run or idle. This qualifies as a faulty sensor, correct?
For posterity I pulled the valve off to and the pintle seems to be functioning properly. Now I need to go find a new gasket for it, though. Oh well.
Again, Thanks for the expertly explained and easy to understand information.
~Jon
Code P0401 EGR flow insufficient. is most likely caused by carbon buildup in the path or paths in the manifold. I just fixed mine by cleaning. It was so bad that I had to run a 3/8 drill through them after removing the manifold. Mine was a 4.6 liter V-8 but I understand that the blockage is a common ford problem. PS I spent money on replacing the other parts of the system before I found the real problem. CLEAN YOUR MANIFOLD.
On your post http://free-auto-repair-advice.blogspot.com/search/label/Ford%20EGR in step 2 you talk about the voltage checks and i have done these and think the sensor is not getting power from the computer, a whole new ballgame, how do i deal with this?
Well Kenny, this is where the fun begins. You have to trace this circuit back towards the computer. So you'll need a wiring diagram to find out which pin at the computer connector provides power and test it there. If you have power at the pin, then you'll have to follow the wire and see if it's cut or crimped anywhere.
To get a wiring diagram, buy a one week subscription to eautorepair.
Copy this link into your browser
http://eautorepair.net/?Vid=107177
Hi Rick,
Thanks for the great advice!! Could I trouble you with a bit of a problem I've been having based on your info?
I've been having some trouble with my DPFE for some time now. My car blows the DPFE pipe off at around 3000 revs, chucking exhaust around the engine bay, and it stutters at around 4000 revs. It still runs ok aside from that.
I've had a look at both pipes, which are very clean, the DPFE itself ok but I imagine it has a problem if its blowing off the DPFE pipes. I've secured one of the pipes with a jubilee clip (it was quite loose), yet the other pipe is being blown off.
I've tested the EGR Valve which is showing correct resistance, and I've just tested the DPFE cable as you've suggested.
I disconnected the DPFE and have tested it with the engine off but in ON position, and with the engine idling. The center pin shows 0v (appears to be ground), but BOTH other pins are at 5v, and 5.2v with the engine running.
According to your notes, this is wrong! I've followed the wires but can't see any problems that are obvious, and not much has been done to my car lately.
Is it likely this is the DPFE, is this normal for my car (its a Ford Mondeo 2 litre, 16v Zetec 1997 MK2, UK edition) or something else which is causing the 5v on both sides?
I've read up on a few places about this, which have suggested it's probably the DPFE, but that it also could be the Cat blocked that is causing back-pressure to force the pipes off (they're not particularly a tight fit, but a lot of exhaust is coming out). I've called my local Ford garage who want £250 to fix it, which I'm rather not keen on doing!
Thanks again for your great blog posts, can I trouble you for any thoughts you have?
Thanks again and keep up the excellent work!
Dug Stokes
Thanks for posting my comment Rick, I've sorted the problem; my catalytic convertor had broken up, blocking the exhaust at higher powers, and causing backpressure. Hopefully this will help someone else!
I'm with the guy several posts above. Got a '95 Ford Ranger with the 4.0L engine and can't get the nut holding the EGR Valve to the maifold tube to budge. I've also tried penetrating oil, heat, etc. Just to make sure I'm doing it right, does anyone know for sure which way the nut turns to loosen it? I know lefty-loosey/righty-tighty, but to loosen the nut, does it back off towards the firewall/back of the engine, or does it go forward towards the EGR Valve? This thing is driving me crazy because it's turning an otherwise easy repair into something difficult. Any tips are appreciated.
Anonymous, I've read on another forum that the nut holding the EGR valve has a thread which goes the other way. Try turning it clockwise to untighten it, you might be surprised!
I have no idea why they chose to do this!!
I'm getting the P0401 code and got my truck home after it stalled twice. I cleaned EGR valve and connected tube. Replaced EGR solenoid. The truck want even stay cranked but for maybe 5-10 seconds. Is it possible a bad EGR valve or bad sensor can cause this problem?
hi I have an 2005 escape v6 and the back presure on it is blowing the hoses off and i thinkin fron this forum thatthe cat is clogged and i was just lookin g for some comfermation on this belief. Thanks
Russ.
Hi Rick,
Well you have an excellent website. I have read many of your articles and appreciate all the help you've given us. I was hoping you could help with an issue I am having.
I have a 2001 Mercury Sable showing a P0401 code. At first I was going to just replace the EGR valve but read your article and have been advised against doing so, so I will be checking the DPFE voltage and making sure there is no build up in the system. I want to know if this is related to the EGR itself or possibly something else though.
Upon HARD (pedal to the floor) acceleration usually getting on the freeway the car seems like its kicks out (like a misfire) for a second. The vehicle remains on and then continues to accelerate normally. It is normally from 2nd to 3rd gear but I don't feel like it is a transmission problem. I am wondering if a bad EGR valve would cause something like this? The weird thing is it only happens 4 out of 10 times. I will be following your guide on diagnosing the EGR Valve/Sensor but wanted to get a little insight from you regarding this issue.
Thanks again!
Sam
Do the DPFE voltage tests. If the values are in spec, fine. Otherwise, replace the DPFE--it's the most common failure item on these Fords. After that, pull the EGR and check the operation of the pintle and condition of the port.
Hi Rick,
Hopefully I will be able to test the voltage at the DPFE this week. If the specs are within value then should I assume its the EGR at point? Also I plan on using some carb cleaner and cleaning out the EGR regardless. Does my problem where the car hesitates and kicks out sound like an EGR issue? Just want to double check.
Thanks
Sam
Hi Rick,
Well this is what I got. I went ahead and tested the DPFE Sensor today and I was showing 5v on the brown/white wire and .15v on the brown/light green wire. So I concluded the DPFE was bad. So I disconnected my multimeter and got in the car to head to the auto store to pick up a new sensor. But when I turned on the car it was hesitating and running rough. It seemed like there was a loss in power too. It idled really low and didn't run like it had before I did some testing. I am hoping to get this fixed before tomorrow as I have work and this is the only car i have. This problem is at idle and when the car is driving. Could I possibly have pierced the wire too much and now the DPFE is not getting ANY voltage?
Also I havent removed the EGR as it seems I will have to remove other engine components.
Any help would be EXTREMELY appreciated. I hope I can get this fixed ASAP.
Many thanks to Rick and hello to all,
I try to find an egr position sensor for my ford focus 2002, but so far tried two different types and none of them fit. Basically the plug wouldn't fit in. I thought about just hacking the socket to fit it in, but was not sure if it would work. I mean it should right? they are all for 2L DOHC engine in the end...
Any suggestions?
Thanks
Rick,
Hi..I have been reading the posts and thought I would ask a few questions. I am a weekend mechanic (actually once in awhile..LOL)...My 2000 Ford Ranger 2 cyl failed inspection. Check engine light was on and the diagnostic results indicated a code of P0401. I purchased an EGR valve with the intention of replacing it myself. In reading your article UNDERSTANDING THE FORD DPFE AND EGR SYSTEM it appears there are 3 components: EGR vale, an EVR and a DPFE. Must all 3 components be replaced together?...In speaking with a mechanic he indicated a vacuum selenoid..is this the EVR...any and all advice would be appreciated. The EGR valve replacement looks fairly easy to tackle...Thx...Paul
You do NOT have to replace all 3 components at the same time. The EVR is a solenoid. The computer pulses the voltage to the solenoid. The number of pulses per second determines how far the EGR opens. So if the computer pulses 5 1/10 second pulses, the EGH will open 50%.
Hi Rick, thanks for your valuable discourse on the subject. I crept underneath my 96 Taurus (Duratec v6), cleaned the O2 sensors. With engine idling, I emptied an entire can of carb cleaner into the manifold after the air filter hoping all sensors downstream could be scrubbed of all carbon residue. Newer codes appeared - lean mixture and catalyst system low efficiency. After looking through this post, I went to check the maf sensor and feel the tubes- lo and behold, the vac hose cluster had slid off the air manifold. Note of caution - carb cleaner and rubber do not go well. The rubber got all soggy and soaked in the solvent. I have to replace the hoses now.
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