So I just took my first 600 mile each way towing trip with my 2017 F250 Platinum. What a dream...I'm not towing anything heavy for it, only a laughable 6,000 lb travel trailer, but I must admit that this thing is a DREAM to tow with.

Now that's out of the way, here was my issue. I hadn't refilled my DEF for over 7,000 miles and I showed around 1/4 tank of DEF remaining at the start of the trip. Obviously, towing uses a lot of DEF, but this is my first diesel so I'm still learning.

On the trip back I began getting the "~200 miles until you will be limited to 50mph" messages. (As expected) I continued the drive until it had about 50 miles until it would limit me to 50mph, so I decided to pull in to a Pilot truck stop and refill at the pump. This went off without a hitch (SUPER easy with the nozzle fitting exactly into the fitting for those of you that have never tried), and I filled it with around 6.8 gallons of DEF.

This is where the weirdness happened. I start up the truck and got the message again that I had around 45 miles before I would be limited to 50 mph. I figured this was normal and it just took a little time for it to register it had been filled, so I get back on the interstate. I continued to get the messages every 10 miles until I finally pulled back off the interstate to try and cycle the power. I had about 15 miles remaining.

I cycled the power once and it still didn't work. I began to get worried and cycled the power again. Still nothing...one more time, and the DEF gauge finally started to register it had been filled. It didn't fill up like your gas tank (instantly), it basically went up in 1/8 tank increments until it was finally full in about 20 seconds.

So, my question is, is this normal? Has anyone else ever seen this? Is there anything else I should be doing? I did a quick internet search and found a couple people with older trucks having this issue, but not for a new 2017. I didn't talk to the dealer, but I have the TSP parts for the gas tank on order and will mention it when I take it in to have the parts swapped.

Thanks for the help guys...I don't post much on here, but I definitely check the site daily to see what kind of things others are talking about.

 

I filled mine up when I had about 1/3 left in the tank. I never received a warning I just filled it up on my own but as soon as I filled it up the gauge showed the increase instantly. im not sure if it would act different BECAUSE you got the warning messages(I dont see why it would) but It is strange...

 

My 2015 had the same behavior you describe. If you got into the warning then it took a bit to recognize that you had filled it. Luckily that whole system fell off in a freak accident. I think something similar is going to happen to the new 2017 soon after I get it. The county really needs to fill those potholes.

 

Spoojr,

I was warned about this by a friend with a 2016 F350 duelly. They were towing a trailer full of horses when they got the warning. They barely made it home and added 2.5 gallons of DEF. The next day it went into limp mode and needed to be towed to the dealer. The dealer cleared the code and gave the truck back to them.

I was warned not to let the DEF get below 1/4 mark. I add a 2.5 gallon jug of def once the gauge is at the 1/2 mark.

 

I had a similar DEF discussion with forum member Pocket in a different thread today. It sounds like the 2017 is acting a bit differently than prior years when it comes to how it handles DEF. Instructions to allow it to get low in prior year's owner's manuals are not in the 2017.

I have a bit over 3,000 miles but I've already added 2.5 gallons and have another jug ready to go. The level is currently a little over half. I'm pulling my trailer camping this weekend so I'll probably be ready to add that other jug when I return home.

 

I travelled over 9200 miles since new before I finally got the first 500 miles to DEF empty message. My Edge Insight indicated at that time that I had about 10% left. I went to a Flying J and filled up with 6.9 gallons. I was expecting my Insight to then register full immediately but it didn't. It slowly over the next twenty minutes or so went up one percentage point at a time. After slowly doing this it got to around 45% and then suddenly went to 100%. So the DEF gauge registers in a surprising way. But I like the fact that you do apparently get an accurate percentage full unlike my 2014 and 2012 that only erratically gave 1/3 full or less than half full messages.

 

Before last oil change I ran mine as low as the OP did, complete with all the warnings...and then put 5 gallons in it. Gauge came up about as much as I'd expect (3/4 ish) and the warnings went away. I'm getting quite low again although no warnings yet. So far, operation seems pretty much as expected. I believe the "gauging system" is pretty much the same as the 2011-2016 trucks...with a series of 3 or 4 electrodes located at different levels in the side of the DEF tank. Software estimates the level between electrodes. That is why you need to add more than just a gallon or so to register a difference in level...if the DEF level doesn't rise to at least the point of the next electrode, the system has no way of knowing you added any.

BTW, the reason the electrode measuring system is used rather than a more accurate float system like the fuel tank is because DEF will freeze at 12F and could ruin a float.

 

However it measures, by float or pins, the way it registers through the OBD 2 is very different than my last 6.7s. There appears to be a real time one percent increments of howfull the tank is. If it is still just the pins ( which apparently is the case) then Ford has really improved their algorithm for estimating the percentage full. It still is strange what happens after you fill up.

 

I got the 500 mile warning. I want to say it was at about 1/4 tank. I added 2.5 gallons and it came up to around 1/2 tank. It seemed to register immediately and the warning went away. A little odd that yours had such a delay.

 

My DEF messages have always reset with no issues. I've probably hit at least 4 of these mileage limit messages so far, but have always filled up before I got the 50mph limp messages.

 

Same here for me. I filled a couple of times on a 5,100 mile road trip and got the warning once. I didn't watch the percent full and was only aware that the message went away as expected. The main thing that is different from my previous 2011 is that the 2017 is much thirstier hence the reason for the larger tank. My 2011 would go 5,000 - 7,500 miles on a 5 gallon DEF tank and this 2017 only goes 2,500 - 4,000 miles on a 7.5 gallon tank. This is while towing hot and heavy of course. It doesn't seem to use DEF when empty much at all.

 

LOL< Nice...

 

After hearing the potential issues with the gauge resetting, I fill mine when it gets to half empty. After reading this today, I just went to Walmart and bought some to fill mine back up.

 

I just added a jug of Blue Def to mine. The gauge before filling was sitting slightly above the halfway mark. I added the fluid and about 2 minutes later set the ignition to accessory mode and stared at the DEF gauge. After about 60 seconds it popped all the way over to full in one motion. Going all the way to full seems a bit optimistic since I only added 2.5 gallons, but the truck was parked on an incline (the doors won't stay open) so that could be throwing off the gauge.

 

At about 5000 miles I got the "500 DEF" warning and it kept at it down to about 267+ miles to empty/limp mode. I stopped at Pilot and filled the DEF tank (showed about a 1/4 left) putting in about 7 gallons.
The level came up daily quickly as I recall. Still shows full after another 1500 miles.