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Possible hack for P0401 OBD code: insufficient EGR flow

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Possible hack for P0401 OBD code: insufficient EGR flow

  #1  
Old 03-13-2011, 08:54 AM
artfd
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Exclamation Possible hack for P0401 OBD code: insufficient EGR flow

I have 2001 F150 4.2L V6, A/T with 103,000 miles. Recently its 'service engine soon' light came on. I took it to Autozone to have the OBD codes read, P1401, 'excessive voltage from DPFE'
I did my reading on the proper diagnosis of this code, determined that my DPFE was indeed out far more voltage than it was supposed to. I bought a new DPFE from the Ford dealer. I bench tested the new device's voltage, all was as it should be. I switched the DPFE out in less than 5 minutes, reset my OBD codes, and within 20 minutes of driving the 'service engine soon' light came on again.
Back to Autozone to have the OBD code read, this time a different one, P0401, 'insufficient EGR flow'
Back to diagnosis. Pulling a stiff vacuum on the EGR vacuum input while the hot engine was idling, no change in the engine's operation whatsoever. I had done this exact same test years ago on this same vehicle while I was studying the EGR, that time the engine stumbled and stalled when vacuum was applied to the EGR, which was as it should have been.
So either my EGR has failed or its exhaust to intake manifold tubing is blocked somewhere, most likely at the ports into the intake manifold.
The consensus seems to be that EGR's rarely fail while carbon blocking the ports into the intake manifold is the most likely cause of this problem.
At the moment I don't have the time/money/inclination to replace the EGR, and/or remove and clean the intake manifold, and/or to do whatever else it takes to get the EGR working again.
I found a link somewhere on the internet mentioning that it was possible to fool the OBD & PCM into 'thinking' this problem has been fixed by simply connecting the vacuum supply line from the EGR solenoid directly to the REF port of the DPFE, and plugging off the other connections opened up by this hack.
Then the PCM sends its signal to the EGR solenoid to activate the EGR, but this time the vacuum is connected instead to the REF port of the DPFE, the applied vacuum sets the voltage on the DPFE, a voltage level that then signals the PCM that there is indeed flow in the EGR system, and the PCM 'thinks' all is well with the entire EGR system, so no OBD code is set.
I connected it up that way, reset my OBD codes, and have since driven about 100 miles, with 6-10 starting cycles, and no 'service engine soon' light has come in.
 
  #2  
Old 03-13-2011, 08:59 AM
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Don't hold your breath.

Report back in several weeks and after using several tanks of fuel.
 
  #3  
Old 03-14-2011, 01:19 AM
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Art. respectfully, the system is not that simple.
The 400 series codes are test result codes and not dynamic operating codes.
Said another way, the PCM has test routines that are tried everytime the engine is started as a way to test the operating reliability of the complete system as a way to detect a fault. There is no waitng for a failure to happen on it's own.
The dpfe is only a test results measuring pressure sensor that refers it's findings to the PCM as either pass or fail signal that is compaired to a test result table.
If the report is out of limits for the peticular test the specific code is set.
There are a number of different tests that are done at various times all with different codes.
In addition, the EGR operation does other things that normally are transparent to drivability until a fault occurrs.
1 the ignition timing is advanced.
2. the fuel is cut back.
3. oxides of nitrogen emmissions are reduced by the small amount exhaust gas the EGR allows back into the intake for lower combuston temperatures.
The sum total is a benifit to fuel mileage while reducing emmissions.
Remove the EGR and clean the ports so it all works as it is supposed to.
There is no real 'hack' here that is of any benifit. There is too many things going on as discribed.
Those who think they are getting 'around' some operating system by a so called 'hack' do not understand the way things work and try to pass it along as something lagit that it is not.
Good luck.
 
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Old 03-14-2011, 03:09 AM
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I've done a great deal of reading on EGR systems over the years & never found evidence that the operation or lack of operation of EGR alone affects mileage one way or the other. If the EGR turns on when not called for, the engine may indeed stumble or stall, but that is not my issue. All my references mention that Exhaust Gas Recirculation, when properly applied, decreases NOx emissions at part throttle. EGR is always supposed to be inoperative at idle, so when the engine starts, how can EGR even be tested by the PCM until the engine has warmed and the throttle is then partly opened? I have also read that the modern PCM circuitry will fiddle with the ignition timing and the fuel/air ratio when the EGR flow is inadequate, but that is a different problem, more a problem with the PCM than the EGR, and something I think will indeed decrease fuel mileage as you said. The point of my 'hack' was to keep the PCM from making those unneeded adjustments until I can come up with the $200-$300 my mechanic wants to remove the intake manifold and decarbonize it. I've driven over 100 miles with my 'hack' installed and can't tell anything adverse is going on.
 
  #5  
Old 03-14-2011, 12:02 PM
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dude, 200-300 bucks??? seriously?

here check this out

How to clean your engine's throttle body on your Ford F150

it took me1-2 hours to pull the trottle body and clean it and put it back together and that was with taking a lunch break to let some cleaner evaporat from the lower intake manifold. youll need two spray cans of b12 an old tooth brush 5 or 6 pipe cleaners and a small flat blade screw driver to dig out the egr ports at the bottom of the trottle body. once i got them hollowed out i let them soak for 10 min in some b12, dump, let them soak again, dump, soak, dump and then they were nice and clean. i did leave the egr on the throtle body tho because it felt like the bolts were seized up.

the whole process was very simple and only cost about 20 bucks worth of cleaners and pipe cleaners. so if you have a couple free hours, i would do it yourself and save a bunch of money.
 
  #6  
Old 03-14-2011, 12:08 PM
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actually, just bring it by here, and ill do ti for 150 bucks sweet deal right? ahahaha you save some money, i make some money, you get a fixed truck, everybody wins right?
 
  #7  
Old 03-15-2011, 02:22 AM
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art, repsectfully, you came here for help, I gave you accurate info and still you are not accepting.
Some of your statements shows you need to learn about the Ford system.
For example working on the EGR, the SES goes off then comes back on 2 drive cycles later.
And your statement about no cold test is wrong.
What you saw was the system does TWO tests before setting a logic code for the failure. Did you know that?
There is a reason why it is done that way.
Go to the Motorcraft website and down load the overview for your model and year instead of going other places and reading bits and peices that causes you to form incorrect conclusions.
What I give you is not a bunch of "I thinks or I reads here and there", it's facts.
Good luck.
 
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Old 03-15-2011, 09:25 PM
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the SES goes off then comes back on 2 drive cycles later. I've gone about 8-12 drive cycles, 200 miles, since the hack & the SES light is still off. Then I wondered if the SES light itself had burned out, so I ran the OBD codes, no faults were found.
 
  #9  
Old 03-15-2011, 09:32 PM
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the whole process was very simple and only cost about 20 bucks worth of cleaners and pipe cleaners. so if you have a couple free hours, Oh, I have the time but my experience of removing things from the engine & the manifolds involves having bolts break off instead of being able to unscrew them. I looked at the web page you referred to and my 4.2L engine looks way different from the one illustrated. If I can find a guide with appropriate visual references for the 4.2L (and if the precip ever stops falling over my truck) I will give it a try. I did present my problem with my truck's OBD codes to a local mechanic, he has done quite a few of these decarbonizings, and the $200-300 was the price he quoted me. Of course, he probably also charges 1 hour of labor to replace a DPFE, which takes 15 minutes if you take a coffee break.
 
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Old 05-03-2011, 09:58 PM
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hi i got a 97 ford van with the same trouble po401 ces lite on and replaces drfe and egr and egr valve solenoid still on how are the ports designed into the 4.2 liter manifold?
 
  #11  
Old 05-04-2011, 08:21 AM
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Exclamation Port architecture on 4.2L intake manifold

Originally Posted by amoureman View Post
hi i got a 97 ford van with the same trouble po401 ces lite on and replaces drfe and egr and egr valve solenoid still on how are the ports designed into the 4.2 liter manifold?
I have searched again & again for images of this manifold & illustrations on accessing it, and have not found it on the internet. Have found illustrations for a 5.X intake manifold, but don't expect it to much resemble the 4.2L manifold.
Are you sure your EGR does not function? Have you pulled a vacuum on its control port while the warm engine is idling?
 
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Old 05-04-2011, 08:27 PM
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yes art it works but there is no change in the engines running when i pull a vacuum on the egr; i tested the old one and it worked too so i changed it for nutin; im going to try your suggestion and attach a vacuum line to the dfpe ref port , is that still working for you?
 
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Old 05-04-2011, 08:32 PM
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There is no vacuum on the DPFE.
I'm sure you mean the egr VR solenoid.
If there is no change in engine idle with opening the EGR manully, the path from the exhaust manifold to the EGR or after the EGR is blocked.
If you need to hear the explanation of why, let me know.
Good luck.
 
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Old 05-04-2011, 09:58 PM
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Exclamation

Originally Posted by amoureman View Post
but there is no change in the engines running when i pull a vacuum on the egr; i tested the old one and it worked too so i changed it for nutin; im going to try your suggestion and attach a vacuum line to the dfpe ref port , is that still working for you?
Rerouting that vacuum line I referred to earlier does indeed work to keep the CEL off, but that's all it does. It does not fix the underlying problem, it only fools the engine's computer into 'thinking' the EGR is functioning. I suspect my mileage has dropped since the 'hack' was done, but on the other hand, ever since the hack, I have been using my F150 only for very short trips around town, and I have always gotten my worst mileage under those conditions. I have done very little highway driving since last fall.
The hack did get me through my emissions test, but I have put all my vacuum lines back in their normal positions. 3 or 4 engine cycles later, my CEL came back on, as I expected. My next step will be cleaning out the ports for the EGR.
 

Last edited by artfd; 05-04-2011 at 09:59 PM. Reason: clarity
  #15  
Old 12-17-2011, 06:34 AM
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Exclamation Source of DPFE Hack; Excellent reference for 4.2L EGR port cleaning

This is the web page that inspired me to try the 'hack' I originally described: DPFE Sensor and EGR Information - Focus Hacks
This is the best post I have found, which describes removing & replacing the upper part of the intake manifold to allow access to and cleaning of the blocked EGR ports into the intake manifold. Very specific, many pictures, and a list of the parts that should be replaced (or preemptively serviced while you're at it). I have been looking for this information for the last 4 years!
 

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