For those of you unlucky enough to be out of warranty on your 6.7 Powerstroke diesel engine, which is a growing number every day, this is a guide on changing the EGR Cooler core to fix the diagnostic trouble code P0401. The replacement of the EGR cooler core is called upon in a technical service bulletin released by Ford. If you are out of warranty and you have this code, you may want to take the opportunity to delete the EGR system and remove the SCR system as well. I highly advise against it due to legality reasons, but the EPA has been cracking down on this sort of thing lately. Technically you should not be able to trade the truck into a dealer with a deleted system.
Ford made steps to solve some common problems of the past with this engine. Past Powerstroke engines of the International variety would constantly deposit so much carbon on the EGR valve causing it to stick open or shut, sometimes making removing the valve impossible. This happens because the exhaust gas first gets cooled through the cooler and is allowed to dead end on the colder EGR valve. Ford's fix was to move the EGR valve to the hot side of the system which cured most EGR valve issues. The exhaust gases enter the valve first then pass through the coolers before entering the intake system, but now carbon deposits inside the cooler itself.
If you are out of warranty and you have this code, you may want to take the opportunity to delete the EGR system and remove the SCR system as well. I highly advise against it due to legality reasons, but the EPA has been cracking down on this sort of thing lately. Technically you should not be able to trade the truck into a dealer with a deleted system. The topic of installing EGR delete kits has been discussed endlessly. It is illegal to eliminate or circumvent emissions controlling components installed by the factory on your vehicle, thus only for off-road or racing use. Eliminating it will require the use of a tuner to fool the truck into thinking it is still attached and working properly. Keep in mind that EGR functionality keeps these engines quiet. A good read on the Worth of EGR Deletes.
Flow through the EGR Cooler can easily be checked with an appropriate scan tool. By monitoring key pids you can determine the effectiveness of the cooler. Monitor MAF, EGR Temp, Bypass valve command, and EGR valve command. Set engine RPM to 1200, command the EGR closed and the bypass off. Slowly open the EGR with the scan tool and watch as MAF decreases significantly and proportionally if the cooler is flowing well. The EGR temp will rise so command the bypass valve on. The EGR temp should drop drastically in about 5 seconds if working properly.
Of course, the easiest way to tell if its clogged up is to remove it and see if it resembles this picture of a clogged 6.7L Powerstroke EGR Cooler.
This is not the easiest thing to replace, but don't be scared because it's not that big of a project. I'll describe to you the way I go about replacing it that also will save you time over the regular standard labor time. Be sure to perform this work in a well lit, clean environment with an ample space set aside for disassembling the cooler after removal. Make sure you have all the tools specifically mentioned in my guide or a comparable equivalent along with drain pans for the coolant. Round up all the parts you will need to complete this task.
EGR Cooler Core - BC3Z-9V425-A
Gasket Kit - BC3Z-9P455-A
Motorcraft Orange Coolant
It should be noted that this EGR cooler removal and replacement process is written with the older first generation of 6.7L in mind, but it applies very similarly to the newer ones.