Home > How-To's > DPFE Replacement - Exhaust Gas Recirculation Flow Insufficient (P0401)

DPFE Sensor Replacement / Repair - (P0401)

My wonderful Service Engine Soon (SES) light decided to light-up a few days ago, alerting me of a problem. Oh, great! Called a friend to come over with his OBDII scanner to pull the code. Shoots back with the code P0401. Great, now what do I do? Google (and the forums) to the rescue. After a few searches and reading some posts, turns out most people solved the problem by replacing the (commonly) malfunctioning DPFE Sensor. Call up my local dealer and the part (FoMoCo# 4U7Z-9J460-AA) was available. Cost $30 + tax.

After picking up the part I noticed it was a bit different than the stock 2002 DPFE. The new part is slightly larger. Great! that should give me a few more HP :) (joking guys). Don't be alarmed about the difference, it is the same (improved) part. Next thing to do is swap the bad for the good. If you can start your Explorer without help, you can change the DPFE. No tools are required, bonus! Note: very slight amount of brain cells will be used for this repair

Okay, let's start. First thing to do is pop the hood. If you don't know how, STOP right now and call up your local dealer to schedule the job.

A little disclaimer before we continue: While replacing the DPFE sensor solved the problem in my case, it might not be the same for every P0401. Sometimes it could actually be the EGR Value or other EGR/DPFE related problems.


1. 2.
On the passenger side of the vehicle, near the firewall, just behind the intake cover you'll find the DPFE Sensor as shown above. Here's a close-up. It's a little black plastic box with a grey clip attachment and two hoses connected at the bottom. Remember, the part# on the stock one might be different than the new part.
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To remove, you need to pull up to separate the part from the two hoses. The hoses might come off at the part end or from the lower end. You should remove the two little hoses and check for damage, leaks or corrosion. If damaged, replace them as well. Mine were fine so they'll be reinstalled with the new DPFE. Next step is to remove the connector. Simply push down on the tab and pull away from the DPFE. When pulling, place your fingers on the grey plastic clip. DO NOT pull on the wires.
5. 6.
Here's a comparison shot of both old and new. Do not discard the old part until after testing the new part. If replacing the DPFE does not solve your problem (Service Engine Soon goes away) then the old part might still be good. Reattach the two small hoses to the new DPFE and reinstall. Don't forget the grey connector. That's it! You're done.

Test drive the vehicle and after a few drive cycles the SES light should disappear (if the DPFE was the problem). You can also reset the SES light using the OBDII reader/scanner if you'd like it off right away. I've also heard you could remove the negative battery cable for 10 minutes to reset the PCM.

If the SES doesn't reappear later you'll know the DPFE was the problem.


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