Powerstroke 6.0L Technical Intro Manual
Check out link above for good bed time reading.
P0403 and P0405 are beause the EGR valve was unplugged.
P2284 Is and ICP sensor fault. My guess is that the sensor got unplugged/ beat up or the pigtail has an issue. As I re-read your post I am wondering if you changed the oil or the oil cooler. If you replaced the oil cooler and screen and the little sump under the cooler was emptied you could have sucked air into the HPOP. When you get air into the high pressure oil system it can take some time to work it out. I would take it out and drive it pretty hard for about 20 min and see if that clears the problem up.