p0402 ?

[minivan]

98 3.8 How many possibilities?

[DRW1000]

Originally Posted by minivan

98 3.8 How many possibilities?

47.

[minivan]

what are some of the most likely?

[DRW1000]

Just kidding.....................

I think this is your EGR flow feedback. It has indicated excessive EGR flow This is most likely because:

1) Your EGR is open when it should not be open.
or
2) The DPFE is giving incorrect information to the PCM

If your EGR is stuck open you should be experiencing rough idle.

[minivan]

No rough idle , everything seems to be running great. Decipher dpfe. Thanks.

[DRW1000]

DPFE - Delta pressure feedback exhaust (or something like that).

This device detects the pressure of the exhaust and compares it with the pressure going to the EGR valve. This provides data for the computer that lets it "know" how much flow (or how open) the EGR valve is.

If you get P0402 then the data that is being sent back to the PCM (or better still the data being read by the PCM) indicates that there is more EGR flow than the PCM "wants".

If the PCM detects too much flow it would compensate by shutting off the EGR (it is pulse width I believe) and if the data still indicates too much flow it would keep shutting it down until it got to the point where the PCM was not commanding the EGR on but it was still receving data that indicated that there was too much flow.

There are a couple of different styles and the type that is on my 99 (which may or may not be the same as a 98) is known to fail and has in fact been redesigned.

It is a relatively inexpensive part (about $100 CDN or $80 US).

I would pick up a Haynes if you do not already have one. There is a test for these sensors using a voltmeter and it can verify this as the faulty component before trying the part.

If it is your DPFE it is a very simple job (about 15 minutes on my 99)

[DRW1000]

By the way, we both must have been online at the same time last night as you managed to get a post in in between my 47 (joke) and my real answer.

LOL

[egstasea]

My vote is the dpfe. Particularly if you have the metal one. This is such a common problem that guys regularly have this item on ebay for about $40. Been there done that.

[minivan]

Thanks alot. I hope everyone realizes just how thankful they should be for forums of this nature, mainly how much money we all save. Again thanks and I have wore my haynes manual out and will look it up and go from there.

[DRW1000]

You are correct about the value of these forums...........

By the way........Post your findings/conclusions too. We all learn more from a complete thread.

[wiswind]

If changing the DPFE does NOT correct the problem....
With the engine at idle, remove the small rubber vaccum hose that goes to the top of the EGR valve. There may be a very small amount of vaccum present....but if there should not be very much. If there is, try spraying just a little bit of "Sea Foam" into the hose....with the the engine running at idle. I do not think that this is the problem.....as if the EGR valve were open at idle....your engine would be running rough....but worth checking.

[minivan]

Thanks for all the info. Cleared codes the day they we're read and it has'nt came back on yet! I will follow the haynes man. and check the dpfe as soon as I get a chance. I've been very busy w/work and kids. As soon as I check everything i'll post. Thanks everyone.

[minivan]

I replaced the egr valve and got the code a week later. I guess I will replace the dpfe sensor next, the guy I know at the ford parts dept. said he has replaced his dpfe sens. several times.

[wiswind]

EGR valve does not fail real often...
DPFE is a high failure item....VERY likely to correct your problem.