I'm kinda miffed and upset.
This is not my first diesel. Not my first Ford. But it is my first Ford diesel. I thought I did my homework, getting a low mileage model, with records of maintenance. I made sure to get DEF as per those posting on this list, and also to get additive for Cetane, lubricity.. I have both Hotshots and Optilube on hand. I've added specific ounces when filling up.
I haven't towed yet, as that will be the plan. But I did put about 2K miles on truck after buying it. It was at 1800miles that the engine light came on, right after leaving the fuel station (topped off tank and then with add a 1oz of Hotshot). I thought it was like the gas versions when you didn't tighten the filler cap, noting I have aftermarket locking.
I found another stop and pulled out the Ford book. Seems a solid Engine light means emissions, since it wasn't flashing. And it didn't go out after checking cap. Eventually I replaced the locking back with the OEM I had in the truck. Still no light going out.
I had to get home and all else looked fine. So I made it home, about under 200 miles from VA to PA. Soon as I got home, I grabbed my laptop and OBD cable and ran forscan. Sure enough, one code throughout, the P20EE ... bank 1
I searched here and it wasn't fulfilling. I search the net and youtube, with results from parts cannon like replacing front and back NOX sensors, to SCR to even just cleaning the intake near EGR (See Arod Powerstroke tech talk). While I did get this used, I did plan a full filter change (Air, engine, oil, fuel filters) at necessary intervals. I may go with Aircleaner first and work back like Arod suggested. But the truck only now has 23K miles, up from 21K when I bought it.
I'm not having buyers remorse. I'm confident this is something that can be fixed. While I have a warranty, I don't think it covers emissions, but I will check.

If anyone has had this and got it resolved, let me know. Or if you found threads I missed, post for me to double check. I had a good mechanic, but he doesn't do diesels. Might see if he can get me someone local. Don't trust the Ford dealers near me.
Thanks.

 

First, please, always give the full detail on your truck when asking tech questions.
Next is that that code pops sometimes because there was a hiccup, an interruption or glitch and may be nothing at all.
So, were it me, I would clear the code and see if it comes back before worrying too much.

 

Sorry. Its a 2021 F250 Lariat 6.7l , about 23K miles. No modifications. What more details should I include? Thanks!
I'll try and clear the code and see if it comes back.

 

For what you're dealing with, the info provided helps a lot.

I would say, since it's a NOx sensor, clear and see if it comes back. If it does, dig a little deeper...but usually that starts with looking at fuel trims and what the sensors are reporting, and determine if the NOx sensor(s) are reporting somewhat accurately, and that will steer you toward a resolution.

 

Ah. Thanks. I also realized I should be posting this in the Forscan discussion threads for my model year.