Mothman, That's what I like about you, you're always giving me great ideas to look into. How about the vacuum control valve just a thought. I'm at the point were I'll try anything. Have a good one

 

Someone once said, "If you replace every part, eventually you'll fix the problem."

Why not watch some television for inspiration?

http://www.youtube.com/watch?v=pVcWDkwTxj8

 

That someone must have had alot of money to blow- Video was very interesting

 

Mothman,
I thought the egr valve was closed at idle with the vacuum line connected but it's still open, still running rough when idling or stopped at a light. I had to block the vac line leading to the egr again to have the valve stay closed. I also tried what you said I disconnected the electric leads to the vacuum solenoid while it was running and the egr valve closed ,as soon as I reconnected the leads the valve opened again it's looking more like the ecm since this is my second solenoid that I tried. This truck is driving me crazy. sharky

 

Yeah, Sharky, but at least it's driving something.

So if it's your ECM, but your ECM's not self-reporting that it's bad, is there a way to determine that short of buying a new one and swapping it out? I just don't know about that. I suppose maybe a good mechanic could tell you that, but what would they know besides the code that you're already getting?

Lemmie think about this for a while....

OK, I'm done thinking.

Sharky, you need go out to Harbor Freight, reach into your pocket, pull out a whopping $4.99 and buy yourself a 7 function digital multimeter http://www.harborfreight.com/7-funct...ter-90899.html . Go home, set it to ohms and measure the resistance of your EGR solenoid. It should be between 36 ~ 44 ohms. If it's not, that tells us something. If it is, that tells us something, too.

 

Mothman,
I'm picking up a mutimeter and checking the solenoid Thanks

 

Mothman,
I picked up a mutimeter at the auto parts store. I hooked it up and got a reading of 33.4 ohms. I double ckecked it with my friends mutimeter and came up with the same reading. I wish I knew he had one before I went out and bought one.

 

Don't feel bad. Now you have your own and I'm sure it didn't cost an arm and a leg. Your measurement would seem to have placed it outside the normal specs. Haven't you already replaced this item twice before?

Another thing you could do would be to test the signal coming into the solenoid from the ECU and see how this changes as the engine warms up.

 

Mothman,
It only cost me 15.00 not bad. I did replace the solenoid 2 x alreadly. I'll try to check it again after it warms up. Thanks

 

After reading this post, and doing my own research on it while going mad trying to find anything that would point to why this code would appear after a while, I found the simplest of problems cause a lot of headaches.

The entire EGR system was basically replaced. From valve to controller valves. P0401 would still would come up after a while. I then noticed one of the electrical connection clips was broken! It would slightly slip off while driving but not enough to be fully evident when inspecting it. I used a zip tie and it worked for a while. This was the cause!

I went to a junk yard to find a comparable electrical connection, spliced and replaced. Worked like a charm!

Check your connections everyone -- especially the clips that hold them in place. These connections have to fit snug and will shoot a code if clip is missing and loosens up slightly.

Found that I also had a vacuum leak to EGR. I held the vacuum return line which should engage EGR diaphragm.