F150 v6 4.2L 2001 . Got the dreaded p0401 egr code up . Vehicle idles well , but seems to miss at about 20 mph . So far have changed the plenum seals , as it had a leak . Changed the dpfe . Dismantled , cleaned , and tested the egr valve with a vacuum pump , all good . Their is a slight leak on the egr tube at the nipple on the manifold . How do you check the ports in the manifold , do you have to remove the plenum again . Any suggestions , much appreciated . If you apply vacuum to the egr when idling , engine slows but does not stall .

 

I too have that code as well as the 174, I see there hasnt been much activity here. Have you disconnected batt to reset the pcm and what do you mean you changed the plenum seals?, does your enging have an upper and lower plenum

 

F150 v6 4.2L 2001 - go check the forum for that particular year & model. The P-0401 error code is discussed at extreme length there.