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I have a 2014 F250 6.7. A couple of weeks ago the cold side intercooler pipe blew. I had to drive about 20 miles like that before I was able to get to a place that I could do anything. I was able to get the part and a buddy and I put it on. Truck ran fine. A couple of days later the check engine light came on. I went by AutoZone and it showed a nitrous oxide sensor code. Then the check engine light went off after driving in a little bit. Now I have a DEF system fault message telling me that I have 50 miles before I’m limited to 50 mph. Could these two things be related, or could it be something other than that wrong with my DEF system? What I’m wondering is could the nitrous oxide sensor really be bad and be causing the DEF system fault?
It's possible they're related because DEF is what neutralizes Nox. I would see if you can delete the codes and drive it and see if another code pops up. If you were to replace the Nox sensor, I would highly recommend a Motorcraft part and not some after market part.
I had the same issue about 6 months ago with my 2015. Scan showed NOx sensor fault. Ford has a TSB on this issue. If you get on the Ford website ans enter your VIN it will show any recalls on your truck. Mine had one outstanding that addressed the DEF system fault. Took the truck to a (somewhat) local dealer, had it reprogrammed and the 50 MPH in 50 miles went away. I did replace the #4 NOx sensor before I took it to the dealer, and didn't clear the codes until they could see them. The fault codes were resolved with the reprogram.
Hope this helps, Mark.