I have replaced the EGR valve, the DPFE, and the O2 sensors, cleaned the hose from the EGR to the exhaust and I still get a po401 code.
ANY HELP WOULD BE GREATLY APPRECIATED.
'99 F150 4.6

 

Did you take the throttle body off and clean it out as well? Mine was caked with carbon when my code popped up. Also, how long have you driven the truck since replacing parts? Did you reset the light?

 

You might try checking the gas cap. If I'm not mistaken, the P0401 is
an evap code. The gas cap might be broken and is venting gas out.
Just remove the gas cap and wiggle the end (that sticks down in the filler
neck) if there is any movement, then its broken.

Hope this helps.

Mike

 

P0401 is insufficent EGR flow detected.

You need to remove the elbow between the throttle body and the intake manifold and physically scrub all the crud out from the EGR ports. I use a .22 caliber bore brush chucked up in an electric drill and carb cleaner.

 

Thanks fellas, I have reset the ce light each time I replaced a part. Last night I took off the new EGR and scrubbed out that port and have reset the ce yet again. ( yep loads of carbon ) Luckily my neighbor has the OBD reader that we slapped onto my laptop. I gotta get him a beer or two. I will have to get to the throttle body this weekend. Y'all have one on me.

 

I had code P0401, and it was a bad DPFE (EGR) sensor. I got mine replaced at the dealer for free because I was still under warranty. But I think I heard someone say they were $35 at autozone or advance auto.