I have a 1997 f150 4.6L v8 and the check engine light is on. My friend has a code reader which read P0401 and one that read P0401(pd). According to a book he has it is the EGR valve or a plug of some kind. We replaced the EGR valve. The old one seemed to work fine but had some bypass when the valve was closed so we decided to go ahead and install the new one. We checked the vacuum which seems fine but we were only getting a little flutter feeling on the vacuum line that plugged into the egr valve. So I unplugged it at the solenoid and got the same thing at the their but vaccum line going to the solenoid from the intake manifold sucked like crazy. I called the dealer on the solenoid($37) and they said it's common for the solenoid to go out. If I'm not getting suction to the egr vavle from the solenoid, then the egr will not open. I've checked the vacuum on the egr side of the solenoid both cold and hot and idle and revved and nothing seems to increase or decrease the slight flutter of a vacuum that I might be getting. Like I said, the vacuum line from the intake plugging into the solenoid is sucking like crazy. One other thing, we unplugged the battery while we changed out the egr valve just to reset the computer. When we got done it started just fine but I left take for a test drive and it would die when I came to a stop in drive but would start back up and idle just fine. And when I got out on the highway the lifters would rattle like crazy. I run premium gas only. So 2 days later the check engine light comes back on but now it runs great as soon as the light came back on. I'm thinking it is the solenoid. Parts dept at ford also said I could check the ohms at the plugin but they didn't know the values. Does anyone here know them for open and closed and inbetween? They also mentioned another common part to go out is the Differential feedback sensor ($131). I have no idea what that is. Can any help?
Thanks in advance,
Eric

 

Clean your throttle body ports.

Replace the DFPE if the problem continues.

SEARCH "P0401" for hundreds of identical posts.

Steve

 

Welcome to FTE Eric.


You did not say how much mileage is on your truck. Here is a link to a thread that has a lot of information on this subject. Like project said, you can search this forum with the code from the code reader and you will find more than you want to know about this.

https://www.ford-trucks.com/forums/2...ighlight=P0401

 

I had the same problem on the same year/engine. I took the same steps to fix it to no avail. Finally I talked to a dude at Auto Zone that had a friend that worked in Ford service. He sold me a $7.00 gasket, told me to take the throttle body off and clean out the carbon. I did it and haven't had a problem since. Both dudes got some free beer. Hope this helps

 

I have 80,000 miles on the truck. I looked up those other references and they were helpful. Sounds like the next step might be to take the throttle body off and clean the ports. But shouldn't that egr solenoid be opening up at somepoint?

Thanks all,
Eric

 

It's been awhile since I did mine, and forgive me if I'm not getting to the point you're looking for. I think when you look in the throttle body you'll see how the carbon has not only coated everything, you'll see that it's "stacked". I also seem to recall that there were (two?) ports that provided the vaccum to open the valve. Since the carbon builds up so much I imagine there is the possibility of a chunk breaking off and getting lodged somewhere in the system. I was fortunate and that didn't happen to me. (Personally, I think that is an unlikely scenario) I carefully scraped it with a screwdriver, sprayed it with carb cleaner, dried it and nary a problem. Good Luck