Thanks to this board I have repaired the P0401 EGR code..
This is my wifes 97 Expedition with the 5.4..
Bought a cheap scanner and pulled the code..
Searched the forum and found some suggestions. Tried the EGR port cleaning on the throttle body and found the 5.4s dont have the clogging problem the 4.6 has. Read that in another post after I tried the cleaning,, I should have searched more .. Oh well, the throttle body needed cleaning anyway since the plate was starting to stick again..
Then checked the DPFE sensor and found it was almost corroded shut on both ports with some type of white calcium deposits.. Replace the sensor and the code came back,, so I did a little more searching and found a post about the supply vacuume being low to the regulator solinoid..
Presto,, hardly any vacuume was present.. Traced the tube and found it was broken right behind the battery where it goes into a black rubber disconnect plug.. Repaired the tube and all is well..
Now have the OBDII code scanner to add to tool box..