I have a 2002 F150 with a 4.6L. I keep getting a P0401 code and have isolated it to the DPFE. I bought a new one at Autozone and replaced it and after the 3 start/drive wait, the SES light goes out and the engine runs great for 3 weeks.
The light comes back on and again, it is a p0401. Get a warrenty replacement on the DPFE and I'm back on the road again. I've done this 4 times.

I see the is a TSB on intermittant DPFE's. Did Ford change their specs on DPFE's and the ones at Autozone are not in spec? Do I need to buy the Ford part? Do I have something else wrong that is blowing DPFE's? Once they go bad the sensor voltage is always the same as reference.

Any ideas?

Thanks in advance.

 

Hello Dukey_truck and Welcome to the Forum!

That is a interesting issue you are having. Hold on and someone will be along with the answer.

Enjoy the site!

 

Uh, have you done ANY diagnostics to pinpoint the fault?

A P0401 code can be caused by at least half a dozen different things, the DPFE being only one of them.

Steve

 

You don't say what the mileage is on your truck. Here is a thread with a lot of good reading for you!

https://www.ford-trucks.com/forums/248921-diagnostic-code-p0401-insufficient-egr-flow.html?highlight=P0401

Pay particular attention to cleaning the carbon out of the EGR ports. Take the EGR off and the throttle body off to find the blocked ports. Clean it out real good. Good luck!

 

Dukey,


I had the same problem on my 2001 screw 4.6. It was the carbon in the EGR ports just like King said. I used a coat hanger, several diff. size drill bits and screwdrivers to clean the carbon out of the ports. You have to take the TB apart, but not a hard job. I would spend the time to atleast check that before getting another DPFE sensor.

Hope this helps

 

Sorry, I didn't post my mileage. It has 40K on it. I have cleaned the throttle body and tested for blocked EGR holes. I also replaced the EGR valve. By the info on the P0401 threads, it sounds like I need to get a genuine Ford DPFE and try that. I have not run any diagnostics. When the original DPFE failed it came up with a P0401, P0402 and a 1402 I think. All these pointed to the DPFE and when I replaced it, it fixed the problem....for 3 weeks. I've been replacing them and refixing the problem since. Just trying to get ideas for something I may have missed. Thanks to all that have replied. I'll repost if the new Ford part fixes the problem but it will be at least a month from now

 

So where is this sensor located?

 

You might also want to check the vacuum hoses to the DPFE. Mine were cracked near the throttle body, but alligned so that the break wasn't obvious.

 

I also suffered the frustrating P0401 code for several months. I have a 98 Expy with 94k miles on a 5.4L engine. After checking for plugged throttle body ports, replacing the EGR valve with an Autozone unit, and the DPFE with a new model Ford unit, the problem persisted. Thanks to help I received on another thread in this forum, I was directed to some suspect vacuum lines, which were indeed broken. I repaired the vacuum lines, and I have not had a problem since. In the mean time I have logged about 700 miles over several weeks without generating the P0401 code. Definitely check the vacuum lines.

 

The problem is it is thought to be to simple an operation when it's quite involved.
Here are the parts involved.
The EVR regulator, the EGR valve, the vacuum hoses they operate on, the DPFE, the stand pipes, the electrical connection to the DPFE and EVR and the total path..
The codes only tells you what system is involved not what part is faulty.
401 code is the DPFE detecting low flow.
The 402 code is to much flow.
These tests are done at different times under different conditions.
A complete inspection and testing are needed to be sure nothing is missed or the codes will hassle you until you have some luck.
The next part is explaining how the tests are done so it all makes sense.
It's a lot of typeing.
Just a little of it is as follows; the 401 code is tested after the regular EGR testing passes, other wise low flow testing will fail anyways.
Low flow tests the pressure drop across an internal EGR tube restriction. Is it blocked?
402 code is an excess flow test done just after startup and acceleration in lower gears. How it's done. The DPFE looks at the EGR tube pressure with the EGR "closed" making sure the EGR pipe and closed EGR hold pressure. This is the excess flow detection it expects "not" to find otherwise the tract is faulty.
It's all program software driven hardware and no about, close or good enough wiil do.
It is either good or no good within narrow limits.

 

Sorry to get back to you so late. I found the problem to be a bad vacuum line from the egr control to the egr valve. Specifically the boots that are at the end of the plastic tubes leak. I put some RTV around he boots and that fixed the problem for awhile. I recently replaced the line from the manifold to the controller and to the valve with 1/8" rubber hose. I have not had a problem in a couple of weeks and the truck runs strong. I had to clip the plastic line and the manifold and put the rubber hose over it because of the multiple connection. Hope this helps some.