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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.


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    1. High_Order1

      High_Order1 Active Member

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      .....and, in the beginning of 2005, they started bolting the dpfe to the top of the egr. No more just buying the dpfe, you hafta buy the entire high-dollar assembly. :(


      -Shawn
       
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    3. Nebraska Ranger

      Nebraska Ranger New Member

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      DPFE and P0401

      I would like to thank those for posting all the good information on this thread,
      Especially ExplorerDMB,and wildbill
      I have just replaced my D.P.F.E. for the 2nd time in 19 months, i bought it from AutoZone in late October of 2006, fortunately it was under warranty (2 years) and I was given a replacement, I'am very interested in the water vapor and acid build up in the E.G.R. system, I run E-85 exclusively in my Ranger, and anytime somebody mentions water as being a issue, I listen!

      So is there a way to prevent or drain/clean the system periodically to stop these expensive little sensors from failing? or am I barking at the moon?

      Thank-You Again!!:usa:
       
    4. cmt08

      cmt08 New Member

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      this thread has been very helpful. Thank you all. I have an 02 explorer and when I turned on the ac one day the service engine light came on, advanced auto scanned it and said it was an egr insufficient flow. everyone at advanced auto said clean out the valve, everyone here says to replace the sensor, and everyone at ford never heard of that even being a problem. LOL! I am not to engine smart so instead of the valve replacement it sounds like i should replace the sensor first. my only questions is if i unhook my battery for ten minutes is that good enough to reset the computer or do i have to delete the codes with a scanner? i did the battery thing once and the light went off for about twenty miles and then came back on.:rolleyes:
       
    5. cmt08

      cmt08 New Member

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      ok I bought a aftermarket sensor at advanced auto for thirty dollars and put it in today, it took a whole ten minutes. when i started the truck it seemed to idle better and the service engine light was off, but i contribute that to the unhooking the battery. well i will drive it for awhile and see what happens. i hope that was the problem and now it is fixed. if not then i will check the egr valve next.:bsnicker:
       
    6. joutlaw

      joutlaw New Member

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      Does a 2005 VIN K Explorer have a DPFE?

      A friend of mine is getting P0401 and P0402 on his 2005 VIN K.

      I'm trying to find the part but not having much luck at NAPA, Autozone, Advance, or O'Reilly's.
       
    7. cmt08

      cmt08 New Member

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      are you asking about the egr or the sensor. what part?
       
      Last edited: September 9, 2008
    8. cmt08

      cmt08 New Member

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      It should. If you are getting the codes then you have an egr, then you also have to have a pressure sensor to go with it. mine is a 2002 xlt so I would think your friends would be no different. I do know all models in that year had a egr valve. Try asking for an egr pressure sensor, I know it is called a couple of different things. if all that fails then get a price check on an egr valve and see if the computer shows a sensor that comes with it. And I did fix it. it was only the sensor. I was kind of hesitant because the rig has 95xxx on it and I thought maybe the the egr was gummed up and had to be changed, but after I changed the sensor the light went off and never came back on. And I did not even reset the computer, the light went off on its own. So glad I found this site, I saved $400+. Again, the part was only $32 at advanced auto in Elk River MN, and it took 10 minutes to do.:D If you still cant find the part let me know and I will give you the part number off the box of the one I bought.
       
    9. joutlaw

      joutlaw New Member

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      Thanks CMT... if you don't mind.. what were those part #s...

      Here is what I posted in another thread...

       
    10. Cooldave52000

      Cooldave52000 New Member

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      I can't find the DPFE Sensor

      I have 2002 Ranger XLT 4 Liter with 48,000 miles the error code is P1400
      I have looked for the sensor but I can not find it.
      Any clues or pictures would sure help
      Thanks
      Dave
       
    11. cmt08

      cmt08 New Member

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      ok guys i will get the number off the box in the morning and post it some time on Thursday.
       
    12. PapiBigRed

      PapiBigRed New Member

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      04 v6 egr

      Am I totally insane or is the the EGR and DPFE all one piece on an '04? Is there a way to test the DPFE?
       
    13. traveler

      traveler Staff Member Moderator Elite Explorer

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      Ok, I know this is an old thread but I didn't see the answer I needed. I've replaced the DPFE, and the code is back in less than a week. So what is the most likely next candidate? The EGR valve itself? Really need to get this code gone as I'm moving to a state that requires a test before getting a tag. Good Ol' Kansas doesn't care if its throwing a code, smoke, noxious fumes, whatever, so long as the car isn't listed as stolen and you have insurance, you're good. lol
       
    14. Turdle

      Turdle Will cook for gas Staff Member Moderator Elite Explorer

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      copied from this link

      http://www.samarins.com/diagnose/p0401.html


      "One of the common problems with many Ford vehicles that can cause the trouble code P0401 is a bad or damaged DPFE sensor (DPFE stands for Delta Pressure Feedback EGR). When diagnosing the code P0401 on a Ford vehicle, the DPFE sensor and the hoses to the DPFE sensor are usually tested first. The DPFE sensor and its hoses should hold the vacuum; the hoses should not be cracked or restricted. The sensor signal voltage should change when the vacuum is applied. Sometimes the DPFE sensor hoses could be reversed during a repair and this also could cause the code P0401. Often, replacing the DPFE sensor with an updated part could solve the problem, however, other components of the EGR system also need to be checked. This thread shows EGR system components in the 2.3L Ford Ranger.
      - The EGR valve could be sticking or the EGR passages could be restricted; both issues are very common. The EGR ports in the throttle body clog up very often too. If you are replacing the DPFE sensor, make sure the hoses are installed correctly and not crossed"

      My suggestions.

      Make sure the hoses are not blown out. They will often split or blow out near the connection to the dpfe. They can also blow off after heavy acceleration. If so, there might be a low flowing cat.

      An exhaust leak on the passenger side will cause a p0401 due to the escaping exhaust pressure. The DPFE reads a differential of pressure between the 2 hoses so any leak will cause a lower reading there. (thinking of the broken bolts on the manifold ----)
       

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    15. traveler

      traveler Staff Member Moderator Elite Explorer

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      I'll double check for an exhaust leak, though I haven't heard one I suppose there could be one small enough to be masked by the louder muffler and tire noise. Also will check the hoses, though when I replaced the DPFE sensor they seemed to be in good shape, still pliable, not brittle, etc.

      Off topic, the need to get to KSrocks in June just increased ten fold. The house has sold and closing is June 30th. So i'll be loading up a U-Haul on the 29th, signing papers the morning of the 30th and driving to AZ the same day!
       
    16. Mainman407

      Mainman407 New Member

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      Btexpress;
      While this DPFE discussion probably old hat, I have been experiencing a similar issue on my 96 Explorer XLT. Some time ago I had my EGR valve replaced. I think they also replaced the EGR valve regulator as well. Anyway, after installing the new EGR valve my vehicle ran rougher than a cob; I barely made it home. The next day I drove back to this shop and told them to replace the new EGR valve with the one they removed only to discover that the "new" EGR had a defect. Well about two years later after constantly being reminded by the 'Check Engine" light I decided to replace the old EGR valve. After installing the new EGR valve and checking the vacuum with a vacuum gauge to make sure the diaphragm was working properly, I cleared the P0401 DT code only to have it return 5 to 10 minutes later. I checked for any vacuum leaks but found none. The next culprit was the DPFE sensor. My DPFE sensor is nothing like the one in your photo. My DPFE sensor has two vacuum ports, so I tested each of the vacuum lines with a vacuum gauge All I saw on the gauge was some fluttering. In other words, no vacuum was reflected; and that was on both vacuum lines. I had REF voltage on the DPFE connector, however.

      My understanding was that the DPFE sensor sends a pulse to the EGR valve and tells the EGR valve to open or close.
      So, with no vacuum being shown from either of the DPFE vacuum lines, could this indicate that the DPFE sensor is bad?


      "ExplorerDMB, post: 1491458, member: 22915"]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[/QUOTE]
       

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