1. for access to Ford Explorer and Ranger owner generated reviews and discussion, tech tips, how to articles, off-road modifications, events, and more! Since 1996 we have been the #1 Ford Explorer resource on the Internet. We also cover the Explorer Sport Trac, Mercury Mountaineer, Lincoln Navigator, Mazda Navajo, Mazda Pickups, and the Aerostar.

    Register Today It's free! This box will disappear once registered!

Diagnosing DPFE Sensor (P0401 and P0402) with Scan Tool

Discussion in 'Tips and Technical Info posted by Technician's' started by ExplorerDMB, August 10, 2006.

  • Searches ExplorerForum.com
    1. ExplorerDMB

      ExplorerDMB Moderator/Technician Moderator Emeritus

      Joined:
      January 26, 2004
      Messages:
      6,209
      Likes Received:
      1
      Trophy Points:
      0
      City, State:
      Mechanicsville, Virginia
      Year and Model:
      2004 Acura TL
      Fords have an issue with their (Differential Pressure Feedback Exhaust Gas Recirculation [EGR]) DPFE Sensors. The DPFE sensor regulates how much exhaust runs back into the system for emissions reasoning.

      Now, this is what it looks like:

      [​IMG]

      If you notice the sensor above it is metal/aluminum. Now metal is a good conductor for heat, so when hot exhaust gas is passed through it, it eventually messes up the insides. This is why a DPFE issue is so frequent.

      Ford tried to fix the issue with a plastic DPFE:

      [​IMG]

      They last just as long as the metal ones. The voltage for the sensor (which can be found under Live Data or Data Stream in a scan tool) should be around .55-1 volt at idle. Anything higher and it should be replaced.

      If you can graph out engine vaccum and the voltages you're likely to see, it would look similar to this graph:

      [​IMG]
      courtesy of rockledge

      The most frequent codes with a DPFE sensor issue is a P0401 and/or a P0402. These mean following:

      P0401 Exhaust Gas Recirculation Flow Insufficient Detected
      P0402 Exhaust Gas Recirculation Flow Excessive Detected


      Now with the scan tool (I used a NGS on my last DPFE situation on a '01 Ranger 3.0L) you can verify your voltage at idle. The voltage I had was a little over 2 volts at idle. And I had the two above codes in the system - with only the 402 code coming on with KOER, but the P0401 was in continous/current codes.

      If you unplug the sensor and the voltage reads 5.0 volts - then this means that your circuitry is good and that a sensor is needed.

      Hopefully that helps some people. :thumbsup:


      -Drew
       
    2. Support EF


      Join the Elite Explorers for $20 a year

      Explorer Forum has probably saved you that much already, and will continue to save you money as you learn how to diagnose and fix problems yourself, and learn which modifications work without having to experiment on your own. Elite Explorer members see practically no ads, add your own profile photo, upload photo attachments directly to your posts and Media Gallery, create more private Conversations, and more. Join Today. Your support is greatly appreciated.



      to hide adverts.
    3. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

      Joined:
      November 11, 2005
      Messages:
      50,938
      Likes Received:
      22
      Trophy Points:
      58
      City, State:
      Brooklyn, NY
      Year and Model:
      88 89 93 95 96 Aerostars
    4. Glacier991

      Glacier991 EF Tranny Guru Moderator Emeritus

      Joined:
      February 8, 2003
      Messages:
      9,830
      Likes Received:
      4
      Trophy Points:
      38
      City, State:
      Sacramento, CA 95827
      Year and Model:
      1992 XLT
      Nicely Done Drew.
       
    5. wildbill

      wildbill New Member

      Joined:
      August 15, 2006
      Messages:
      18
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      Canyon country
      Year and Model:
      1999 Moutaineer 5.0L
      In response to the post about DPFE sensor.
      Being I work for the company that designed and manufactured the sensor for Ford Motor Corporation I cannot mention the company name. I think I need to add a few statements and clarify some problems here. I am a design and failure analysis engineer for this project that is no longer in production. As stated it is a differential pressure transducer that is designed to read the difference of pressure across the EGR valve opening. You have stated that “heat was the cause of the electrics failures” well that is not true the internal sensor and the electronic are made of ceramic and high temperature solder designed to work at temperature above 150C. The 1500C exhaust stream does not pass through this transducer the pressure applied to the sensor is a dead head so the thermal transfer is contained to the stagnant air trapped in the hoses to the sensor that is very slow to transfer heat. The real cause of the failures is water and trapper acids in the water. Ford did a poor job of preventing the build up of water in the EGR system which ended up corroding the inner seal glades of the transducer and allowing the water and acid to come in contact with the electronics as you a know water and electricity do not mix. The biggest cause of the failure was do to short trip driving which did not allow the water to be removed from the system and a build up would happen at a higher rate.
      The graph that shows engine vacuum and sensor output voltages is not complete. Being this is a differential pressure transducer it is designed to read a pressure difference. Being there is a high and low pressure port if the pressure on both ports are equal the transducer will read .500 VDC but if the pressure is lower on the low pressure side the transducer will produce a linear increase in voltage. So if the EGR Valve opens the output goes higher 4.500 VDC Max because the pressure has changed and is lower. When the EGR valve is closed the output should return to the .500 VDC range because the pressure is equal again. I could go farther but that is the premise of how this transducer works on this system.
      Now the second transducer plastic was a second source for these transducer and they had a higher failure rate then the Aluminum housed transducer. The plastic housing was to reduce cost of this transducer not to dissipate heat in fact the plastic transducer would melt with pressure leaks
      .
      The sensor has had a very good track record over the years there were over 4 million sensors produced a year for 5 years and the return rate was 10 parts per million which is pretty dam good being these transducer have to last at least 100000 miles without failure in a very nasty environment.
       
    6. Glacier991

      Glacier991 EF Tranny Guru Moderator Emeritus

      Joined:
      February 8, 2003
      Messages:
      9,830
      Likes Received:
      4
      Trophy Points:
      38
      City, State:
      Sacramento, CA 95827
      Year and Model:
      1992 XLT
      I'll admit to the nasty environment. I will only say that in my somewhat limited experience, anytime I had an EGR issue in a DPFE equipped vehicle, it was the DPFE that had failed. I have replaced a few in my day.
       
    7. kblackav8or

      kblackav8or Member

      Joined:
      March 18, 2004
      Messages:
      69
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      San Diego, CA
      Year and Model:
      00 Mountaineer Monterey
      So does a 2000 5.0 Mounty have one of these and can it trigger a bogus failed O2 sensor?
       
    8. wildbill

      wildbill New Member

      Joined:
      August 15, 2006
      Messages:
      18
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      Canyon country
      Year and Model:
      1999 Moutaineer 5.0L
      You maybe right that you detected a fault in the DPFE sensor but in 70% of the returned product from Ford the transducers were functional and in operational ranges. Most of the automotive repairs are plug and play so when you replaced the sensor you drained the trapped water in the lines leading to the transducer like a finger covering the end of a drinking straw and the new sensor worked fine. We proved to ford on a test Dyno in our plant that the build up of water was causing fails readings in the transducer. If you looked at the new configuration this day and age the sensor does not see the full exhaust stream it only reads the pressure across a very small port in the EGR Valve no more trapped water.
       
      Last edited: September 7, 2006
    9. wildbill

      wildbill New Member

      Joined:
      August 15, 2006
      Messages:
      18
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      Canyon country
      Year and Model:
      1999 Moutaineer 5.0L
      Most likely No. Running rich or agian water on the sensor is a big cause have you noticed the water dripping from the tail pipe or Fords wonderful wiring harnesses shorting or open condition?
       
      Last edited: September 7, 2006
    10. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

      Joined:
      November 11, 2005
      Messages:
      50,938
      Likes Received:
      22
      Trophy Points:
      58
      City, State:
      Brooklyn, NY
      Year and Model:
      88 89 93 95 96 Aerostars
    11. wildbill

      wildbill New Member

      Joined:
      August 15, 2006
      Messages:
      18
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      Canyon country
      Year and Model:
      1999 Moutaineer 5.0L
      A check valve would make the problem worse you need a much larger ID tube before the Transducer so the water surface tension can not hold the water in place in the tubing.
       
    12. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

      Joined:
      November 11, 2005
      Messages:
      50,938
      Likes Received:
      22
      Trophy Points:
      58
      City, State:
      Brooklyn, NY
      Year and Model:
      88 89 93 95 96 Aerostars
    13. wildbill

      wildbill New Member

      Joined:
      August 15, 2006
      Messages:
      18
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      Canyon country
      Year and Model:
      1999 Moutaineer 5.0L
      Water trap sure if you can find one that can handle the heat and the acids Plus find the room to put it in. But the more volume you add to the system the slower the responce to pressure change which would slow down the computer responce time. The best thing to do is drain the lines every 50,000 mile or move some place with lower humidity .
       
    14. ExplorerDMB

      ExplorerDMB Moderator/Technician Moderator Emeritus

      Joined:
      January 26, 2004
      Messages:
      6,209
      Likes Received:
      1
      Trophy Points:
      0
      City, State:
      Mechanicsville, Virginia
      Year and Model:
      2004 Acura TL

      100% agree :thumbsup:

      Whenever there is a EGR issue on a Ford in the shop - pretty much everyone runs to test the DPFE.

      -Drew
       
    15. kblackav8or

      kblackav8or Member

      Joined:
      March 18, 2004
      Messages:
      69
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      San Diego, CA
      Year and Model:
      00 Mountaineer Monterey
      Where can I get a DPFE? I unplugged mine to see if our Mounty would run any better and it made a noticeable difference. I am searching online for one and haven't been able to find it.
      Kevin
       
    16. aldive

      aldive Elite In Memoriam

      Joined:
      January 17, 2001
      Messages:
      24,727
      Likes Received:
      1
      Trophy Points:
      0
      Year and Model:
      1999 XLT
      Adavance Auto Parts, Auto Zone, but I would recommend a genuine Ford part.
       
    17. kblackav8or

      kblackav8or Member

      Joined:
      March 18, 2004
      Messages:
      69
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      San Diego, CA
      Year and Model:
      00 Mountaineer Monterey
      If I plug both lines of the DPFE, what will happen? Is that a useful means to test because the second time I drove it today it ran horrible.
      You can e-mail me offline or PM me regarding testing of the O2. Really need to get this thing fixed -and soon. Hopefully by the end of the week.
       
    18. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

      Joined:
      November 11, 2005
      Messages:
      50,938
      Likes Received:
      22
      Trophy Points:
      58
      City, State:
      Brooklyn, NY
      Year and Model:
      88 89 93 95 96 Aerostars
    19. wildbill

      wildbill New Member

      Joined:
      August 15, 2006
      Messages:
      18
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      Canyon country
      Year and Model:
      1999 Moutaineer 5.0L
      There you go !
      Read the bottom of page 24 ! Water Vapor !
       
    20. matt987

      matt987 Active Member

      Joined:
      July 10, 2005
      Messages:
      150
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      baton rouge, louisiana
      Year and Model:
      '95 xlt
      you can go to your local autozone and get a DPFE, it will be listed in their computer as an "EGR Valve Pressure Sensor".. i paid a whopping $39.99 (my wholesale price..shop i work at has an account)..compaired to fords wholesale price of $134.99.
      Oreillys does not carry the DPFE.
      and reguarding the Oxygen sensors, if you go to Oreilly's they are cheaper than autozone's. I ended up getting Both O2 sensors Bosch part # 51717--for the 1995 4.0 year model only-- for $91.45.. or like 45 each..
       
    21. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

      Joined:
      November 11, 2005
      Messages:
      50,938
      Likes Received:
      22
      Trophy Points:
      58
      City, State:
      Brooklyn, NY
      Year and Model:
      88 89 93 95 96 Aerostars
    22. AaronSptTrck01

      AaronSptTrck01 New Member

      Joined:
      February 24, 2007
      Messages:
      26
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      Fayetteville North Carolina
      Year and Model:
      2001 Sport Trac
      Do I have a DPFE sensor on my 01ST? and should I drain it? If so how?
       
    23. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

      Joined:
      November 11, 2005
      Messages:
      50,938
      Likes Received:
      22
      Trophy Points:
      58
      City, State:
      Brooklyn, NY
      Year and Model:
      88 89 93 95 96 Aerostars
    24. Tony H

      Tony H Well-Known Member

      Joined:
      September 4, 2003
      Messages:
      1,594
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      New York, Wading River (that's on Long Island)
      Year and Model:
      '91 Eddie Bauer
      Were these on the 1st Gen 'X's? '91?
       
    25. btexpress

      btexpress Active Member

      Joined:
      August 2, 2007
      Messages:
      177
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      Thornton, Colorado
      Year and Model:
      2009 Ford Explorer Eddie
      No, the early nineties had a linear sensor on top of the EGR valve. In my 20 years with Ford I don't recall having DPFE problems until late 90's, then it seemed like a flood gate opened. Whatever caused them to fail, 99% of the time an egr code pops up it is the sensor. Regardless of what AZ or the others try to sell you.

      In my long career I have not replace an egr valve since the late eighties..............
       
    26. btexpress

      btexpress Active Member

      Joined:
      August 2, 2007
      Messages:
      177
      Likes Received:
      0
      Trophy Points:
      0
      City, State:
      Thornton, Colorado
      Year and Model:
      2009 Ford Explorer Eddie
      Someone here is bound to bring up the fact of plugged egr ports on Ford engines, and that is a distinct possibilty on many, although rarer than the sensor problem, and usually on moderate to high mileage engines.

      When diagnosing codes I always rely on what the data can tell me, not just the code. Codes are only a starting point, not the answer to the problem.
       

    Share This Page








    We Support Our Troops!