Ford F350 2016 DEF level had just recently dropped to "less than half full". Now for the first time ever, I get the 50 miles until speed is limited to 50mph. Truck has 45660 miles on it. Naturally am on vacation at Gulf Shores and 350 miles from home and it is Saturday night, tomorrow is Sunday and I am supposed to check out of the state park, which is booked solid. Got the warning exhaust fluid system fault. Once the fault code showed up, oddly then the system no longer said the def tank was less than half full, it said it was ok. I put a new container of change on the warning. Except now I am down to 18 miles until speed limited to 50 mph. Any ideas?blue def in anyway, 2 1/20 gal container. No

 

Some of the last two sentences got mixed up. Should be....I put a new container of blue def in anyway, 2 1/2 gal container. No change on the warning.

 

I had that happen once and after a couple more start ups, it corrected itself. The system get's wonky sometimes. I found, as others did, that you don't fill the DEF tank until you get down to 200 miles or less before empty.

 

waiting until you are less than 200 has always been what I have done.

If I were in your shoes, I run in the hopes it would reset. Got to leave the campground anyway.

 

Well, good news. I went for a drive back to the auto parts store this morning to get some more DEF. Background info...I have been in the habit of driving a few hundred more miles after my def tank shows "less than 1/2 full", then putting in a two and a half gal jug. That fills it back to the top and I have been doing it this way since new. This is what I did yesterday. Just in case it was lower than I thought and because of the warning, I decided to make sure it was full. Bought another jug and it held maybe a glass full before it overflowed. Just as I thought but now at least I knew positively it was full.
So on the drive back to the campground, the mileage goes to zero on the 50 mph warning and now the warning message says, "50 mph limit upon restart". So I decide not to shut it off. Get back to the campground and back up to the fifth wheel, tell the wife to forget everything else and close up ASAP. We hook up and are set to didi-mau right on out of that camp. About ten miles down the road as I am throttling up over the canal bridge, northbound out of gulf shores, the engine service light goes out and a minute or two later the warning message disappears. I didn't shut it off until I got home 360 miles later but it ran fine with no issues and the warning messages never returned. A bit over 46,000 miles and a bit confused about just how long these issues are under warranty. My brother has a Dodge dually and they told him that his DEF system was warranteed until sixty thousand miles. Of course he had a $1200 sensor go out at 62k. It seems as if this "should" be a 100k item since it is emissions but I am going to ask.

 

I'm a bit confused. Exhaust fluid low is a different issue than exhaust fluid system fault is it not? I'd be scanning the truck for any DTC codes if it was my truck.

 

I never seriously thought that it was a low def level, I just had to start eliminating any possibilities. I had not driven the truck a whole lot this summer, only about 4000 miles since early June. We did make a quick trip of about 1100 miles prior to this trip (unloaded) to the beach without incident. So the def that was in the tank was maybe half about a month old and half about eight months old. Maybe it had some crystals that migrated to the def injector....or doing something weird in the pump?? Who knows? I don't have a scan tool, I'll take it by a trusted dealer local to me and get them to scan and clear historic codes. Also will ask them if they have any insight about this problem. I hate this particulate filter....easy miles on the interstate I can get over 19 mpg until the regen kicks in....which wastes at least a gallon of fuel making a blowtorch down my pipe and dropping my fuel mileage down by 1.5 or so. How is that environment friendly?

 

Sounds like you might have had a clogged DEF injector...but I don't know...do you have any codes stored?

 

I ran by my local Ford dealer and described the issue and what had happened. He didn't even bother reading it to see if it had a code, he said it is most likely the sending unit in the DEF tank going bad and that they had replaced a lot of the. Said it was covered in warranty and to bring it back in next week and they would take care of it. Yay for me!

 

That's an interesting outcome. We don't see a lot posts about issues with the DEF heaters in the 15 and 16 trucks

 

He said the sending unit, not the heater.

 

Sending Unit/Heater both are the same thing. There are 4 main parts to the DEF system. Tank, Heater, Pump, and Injector, and of course the wiring and hoses.

 

dirthawg is correct, Ford specifically names the part a reservoir assembly.

https://parts.autonationfordwhitebea...OC1kaWVzZWw%3D

 

Super! I was thinking the sending unit was the piece bolted onto the top of the heater assembly. The piece that has all the wire bundle connectors on it.

 

Well, finally got around to getting my truck into my local Ford dealer. They replaced the DEF sending unit assembly and cleared my code that it generated when the CEL came on. I also mentioned the hack about adding the ghost screen that shows the DPF full percentage on the gauges screen. I copied the steps down from when I read the post and gave it to him. They turned that on for me and it works great. Mine was showing 65% full.
No cost to me for anything. Zero, nada. I wish all dealers were as accommodating.