today while driving my service engine soon light came on, I got a little nervios but the truck didnt seem to do anythign differnt still ran good, idled good, accelerated good. So when i got to my destination checked under the hood didnt find anythign unconnected, but I did find the my gas cap wich is a locking one, loose. I couldnt tighten or turn it so it wouldnt just come off easliy. I know the code is EGR and last summer i cleaned all the passesges and everything I have a 01 4.6 with 53.000 on it never had any problems. Just asking if a loose and bad fuel cap coudl throw this code????

 

If the ports are clean, chances are the Pressure Feedback Sensor (DPFE) is bad. It's very easy to replace and should cost about $65 for your model. One thing to remember is that the hoses going to it are not the same size. One is large and one is small (Input/Output). Your original sensor may have the large one on the left, but the new sensor may have it on the right. Put them on backwards (which is easy to do), and you'll still get code 0401.

The EGR valve could also be bad and would set you back about $50.

Whenever I see code 0401 in a 4.6L, I just replace DPFE after cleaning out the ports. It tends to go bad the same time the ports get clogged.