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There has been a lot of talk about the DPFE sensor going bad so I thought I would post a "how to" test the sensor. You will need a volt meter, safety pin and a 3 or 4 ft piece of hose (about 1/4" ID). If you know where the sensor is located skip to the next paragraph. Remove the black plastic cover (3 screws) exposing the throttle body and other fuel related things. Its the cover in the center of your engine that says something like 5.4L or 4.6L on it. Now the DPFE sensor has 2 rubber hoses (about 3/8" dia) coming off the bottom leading in to 2 metal tubes which are leading into a 1" metal EGR pipe coming off the exhaust manifold. On the side of the sensor is a 3-wire connector. This assembly is the DPFE sensor.
Remove the 2 rubber hoses from the bottom of the sensor. Attach a piece of rubber hose to the forward most hole in the sensor. Now carefully take a small safety pin and stick it in behind the top wire parallel to the wire. You do NOT want to pierce the wire, only make contact inside the connector. This top wire is the active feedback signal wire. It will vary from 0-5 volts or so. The middle wire is ground. The bottom wire is 5-6 volts supply. Now the top wire voltage will vary as the pressure between the two holes in the sensor varies. Set your meter to read volts, either turn the key until the accessories are on or start the engine, either way is fine. Now using your mouth apply suction to the hose and you will see the voltage change from near 0 to near 5 if you apply enough suction. The vacuum on the hose should hold your tongue and not leak. If the voltage does not vary or is stuck high or low, the sensor is bad. Do the same thing to the rear port but the voltage difference will be much less, this is the reference port.
If the sensor seems to be working then you can further test the system by doing the following. Attach the hoses to the sensor as normal. Now remove the rubber vacuum hose from the top of the EGR valve diaphragm. With the truck running apply slight vacuum to the EGR valve and this will open the EGR valve. When the valve opens you will see the voltage on the top wire of the DPFE sensor change indicating flow. When the vacuum is applied your truck should stumble or almost stall indicating the EGR valve has opened which it normally does not do at idle. I hope this helps.
DPFE - Differential Pressure Feedback sensor. It meassures the flow in the EGR tube and converts this to a signal for the computer. When it goes bad the performance and milage of your engine will drop.
It depends on how it fails. The sensors voltage is checked at power on for a stuck high condition, this will be reported if it exists. I can't remember if a stuck low is reported or not. At idle there should be no flow and the output of the sensor will be very small, in the few 10ths of a volt range. Basicaly it needs to sense the preasure in the EGR line indicating flow. Its pretty easy to test, just test it to be sure it is outputting a voltage in response to your applied vacuum simulation. At idle should be near 0 volts. If not then the sensor is bad or there is EGR flow at idle and that is also a problem.
I am not an expert but i don't think it could cause any idle problems. The DPFE tells the computer how much EGR flow there is so it can adjust the amount of vacuum applied to the EGR valve thereby opening or closing it more/less. However, at idel the EGR valve should be fully closed reguardless. If the DPFE senses flow at idle i would 'think" this would cause some sort of fault code to be generated. I had a intermittent rough idle problem and it turned out to be a bad IAC (Idle Air Control) valve. The acutuator would stick, I probably could have cleaned it but i just put on new one. Don't know if this is your problem but you could check it.
Thanks Reuel, It Been A Long Check On This Truck And This Site Is Helping Me Out Alot. We All Love Our Fords But As The Computer Tech Increases We Think What The Hell Is Going On .
hey this site is great thanks for the info...my 99 expedition with the 5.4 is chugging at 30-45 mph when bairly on the gas..one of the hoses on the dpfe was off and i reconnected it but still does it, ijust did a full tune up and checked all coils ans replaced the fuel filter...what do you think?
hey this site is great thanks for the info...my 99 expedition with the 5.4 is chugging at 30-45 mph when bairly on the gas..one of the hoses on the dpfe was off and i reconnected it but still does it, ijust did a full tune up and checked all coils ans replaced the fuel filter...what do you think?
Hoses blowing off the DPFE sensor is usually due to excessive exhaust back pressure.
A restriction in the exhaust is the usually problem.
Take your truck to an exhaust shop and have them flow test the exhaust. you probably have either a converter that has melted/crumbled or a muffler that has collapsed internally.
Either will cause you running symptom and the blown-off hose.
hey this site is great thanks for the info...my 99 expedition with the 5.4 is chugging at 30-45 mph when bairly on the gas..one of the hoses on the dpfe was off and i reconnected it but still does it, ijust did a full tune up and checked all coils ans replaced the fuel filter...what do you think
Hi
I recently changed the plugs and COPs on my 99 Expy and it ran like a champ. A few weeks later, I am having the exact same problem you are having. Did you ever determine what was causing the problem?
okay i read everything here and i dont understand what to do
i got a p0402 code which is egr overflow and i had been noticeing slight power drop so i changed egr valve and cleared code and it ran much more stronger and it lasted for 2 days and the code came back up but my truck is running strong.
from what i read on the internet if its flowing to much it would idel rough and have a loss of power and mine does not have either but its got the code again.
so i was woundering what the problem could be and if someone could help me out thanks
No Start, evidently not having injector pulse? Feul pump runs continually with key on and scanner will not see the EEC and check engine light stays on constantly when key is on trying to do a self test! Good spark & 40 psi fuel pressure.
Can anyone help?
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How to test your DPFE sensor.
On This Truck And This Site Is Helping Me Out Alot. We All Love Our Fords But As The Computer Tech Increases We Think What The Hell Is Going On .
