Just wondering if anyone could help me out here, I'm in limbo and don't know what else to do! I have a 2006 f350 6.0 and recently just replaced my egr cooler with one from xdp $275+ and a new egr valve from ford $300. Prior to doing this I was getting a p0405 code so that made me go ahead and replace system! Well system has been replaced and I keep getting a po401 code and can't figure out what is going wrong here, egr cooler along with valve are brand new and my cel light keeps coming on! Any help I'd appreciate it.. thanks tim

 

Not sure if 6.0 has it but Check your DPFE sensor ,
black box with 2 rubber hoses hooked to it . If it was unhooked to install egr valve you may have crooked the 2 hoses when putting together, also make sure hoses are clean inside so air can pass thru .
Differential Pressure Feedback sensor