I got one for you guys i have a 2002 F150 SC 4.6L 36000 mil i went and put gas in when i left i got the famous P401 code cleard the code everything was fine just put gas in and got the same code again and no i have not cleaned the EGR valve yet but a friend said he had the same problem So What Do You Think ?

 

My p0401 was a bad DPFE Sensor. It happened at about 34,000 miles on my 3rd Gen 2001 Screw.

I could clear the code, and it would re-appear after several miles.

Go to a gas station that does inspections/emissions testing, they usually can test the gas cap to see if it is bad.

 

or go to a dealership and have them put in your free dpfe sensor.

then if it comes back on you can clean your egr port.