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EGR Problem Code P0401

Tiny
RJOHNSN1
  • MEMBER
  • 2004 FORD EXPLORER
  • 4.3L
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 165,000 MILES
I have a 2004 ford explorer 6 cylinder. I need to get the car registered, however the check engine light is on. I checked, and the code is P0401 Exhaust EGR flow insufficient. I have been bad and running it below a quarter tank on average for the past year. When I start the car, it idles rough and sometimes shuts off. I decided to fill the tank to ¾ and the car stopped its rough idle within a few days. I need to get this car smog asap. Any idea as to the source of the P0401?
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Tuesday, February 23rd, 2016 AT 2:06 PM

6 Replies

Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
That code is for low flow through the EGR system. There are a number of things that can cause that but the most common on that vehicle is the DPFE sensor. (Differential Pressure Feedback EGR). They fail on nearly every single vehicle. Another name for it is an exhaust pressure transducer.
There is also a passage through the intake manifold that has to be kept clear.
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Tuesday, February 23rd, 2016 AT 4:27 PM
Tiny
RJOHNSN1
  • MEMBER
  • 4 POSTS
Thank you! Although there is no DPFE sensor on the '04 models. It is built into the egr as one unit. I removed the EGR and it is clean, no buildup. I probably should have tested it before. With the low end idling in mind, what else should I check?
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Friday, February 26th, 2016 AT 7:31 PM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
There is a passage the exhaust gas takes between the valve and the throttle body. On some cars that passage has spots that get very narrow and clog up with carbon.

Here is a diagrams and a video to help you check the valve.

https://youtu.be/DqUCbbKdWf4

Check out the diagrams (Below). Please run this test and get back to us.

Cheers
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Friday, February 26th, 2016 AT 7:39 PM
Tiny
RJOHNSN1
  • MEMBER
  • 4 POSTS
I removed the EGR, shook it. The valve was not stuck and moved freely. I also removed the throttle body and intake, cleaning them with carb cleaner as well as replacing the air filter. The check engine light went away, only to re-appear after 20 miles of driving so I replaced the EGR valve and now everything works great!
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Monday, February 29th, 2016 AT 10:15 AM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help

Cheers
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Monday, February 29th, 2016 AT 11:24 AM
Tiny
RJOHNSN1
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  • 4 POSTS
I love this site, all free, you guys are doing gods work
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Monday, February 29th, 2016 AT 11:35 AM

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