Well you can remove the EGR and see if the button portion is stuck. The button is the valve and should open up/close easily if you press on it. If its stuck open or closed, then it needs cleaning. Try to keep the cleaner from getting inside the part especially if you use something harsh like carb cleaner. Do a search on EGR and you should find a nice write-up with pics on how to properly clean the thing. I don't think that a bad EGR will prevent the truck from starting though. Are any codes set?