OK, I had the 50 mph speed limit message on my dash and the truck would only do 50mph. So, I posted in another thread that I was falling out of love with this truck as it's getting old having DEF and DPF issues.

So today thanks to a couple of people on this site I decided to change the def fluid. Well, I looked and wasn't ready to drop the tank guard and mess with all of that so I tried to siphon the def from the filler. So, I can tell you there is a ball or check valve somewhere in the filler neck that won't allow a very thick in diameter hose through. I had some old plastic refrigerator ice maker water line and was able to push it past that check ball.

Now here's the odd part. I removed roughly 9 quarts of def from the tank and the hose was sucking air after that. I figured I should have been around a half tank on the def but the display said def level OK.

I didn't add the new def yet. I checked the display and it still showed def level ok so I decided to drive it and see what happens. I drove it to a car wash, washed it, drove it home for a quick bite to eat and then drove it back to my shop. On the way to the shop I got the 50 mile speed limit message and when I hit OK on the steering wheel the message went out and so did the amber warning icon on the bottom part of the display screen. No more 50 mph limit, no more anything. I checked the def level and it showed under 1/2 full. OK, I thought, it caught up with me I guess. So at this point the error cleared without any intervention other than siphoning some fluid from the tank. It still had old fluid in the tank when the error cleared. I went ahead and added a jug of Blue DEF to the tank and put it on the highway and it runs fine. No check engine, no reduced anything messages, all looks good. I did scan and the P207F error is still in the system and I can't clear it. I am using Forscan to clear it but it comes right back.

So, even though the error is still there I seem to be back to normal for the time being. I am not going to send it into the dealer at this time. I'm not sure what I did but it worked anyway.

Thanks to Just Strokin and Dirthawg for their answers. It helped a lot.

 

you should only do a complete fill after getting the less than 200 miles to empty message. Keeps it from getting confused.

I never add until needed.

 

When I had that code, it was one of the NOX sensors gone bad.

 

That's a very interesting outcome.

If I remember correctly some codes will stay in the computer for xxx amount of days. Since it's an emissions code I bet it hangs around awhile.

Edit: It will remain in the system for 400 days.

 

I remember the day I filled it very well. I was pre fishing a bass tournament at Pomme De Terre lake in Missouri. We were staying in our motorhome one of the state parks and my wife had followed me with the truck pulling the boat down. We had 100 miles or so until empty while at the lake. I developed a kidney stone and that ended our trip. We packed up, headed home with me driving motorhome in some of the worst pain I've ever felt and the wife calling saying the message was 7 miles left. We made it to a truck stop and that's when I filled the def tank. So yes, we waited until the message appeared before we filled it. So yes, it's a day I won't forget nor the 2 1/2 weeks after I suffered until the doctors went in a took it out.

 

So, if I understand your story correctly, you refilled your DEF tank at some point several months ago at a truck stop. It was after that the P207F popped up. Since then you drained around half the tank, drove around, and the problem went away. And then lastly, you have topped off with fresh DEF? And the light is still off, and power is normal? I'd continue to drive and see how this goes. What doesnt make sense to me logically is draining half out, and driving, and the problem went away. If you had drained half out, refilled with fresh, and drove around then I'd say you had a bad/weak/old load of def. DEF is pretty cheap. Maybe drain the entire tank and replace with fresh again, or don't but keep driving and see what happens. If you arent under warranty anymore at this point, then I'd just continue to drive too, and see what occurs.

 

You are understanding correctly. The problem went away with the old DEF in the tank. The only thing I did was lower the level and drive it. I did that only because the display kept saying def fluid level OK. I wanted to see if there was a issue with the level sensors. After 3 drive cycles the def level reset and so did the codes and the error messages. That's when I added a jug of DEF to the tank. When I parked it last night the display did show under 1/2 tank but I thought I would drive a few more cycles before I added any additional DEF. I want to see if it goes from under 1/2 to fluid level OK.

This all happened last November so it wasn't that long ago and the DEF shouldn't have deteriorated that quickly. That and the fact it reset itself with the old DEF in the system makes me wonder what the real issue was.