My first experience with this was a bit frightening. I was driving my 22 Limited to Alaska with my pregnant wife pulling my 5er. In Whitehorse, Yukon, I filled the tanks, 135 gallons, and found a DEF pump to fill, 6-7 gallons. Truck was off as I filled. ABout 80 miles north, I start getting LOW DEF warning. Gage showed full but MTE was down to 100 or so. WTFO? It's not easy finding DEF in Canada and remote Canada is really sparse. As I drove along getting more and more puckered, it kept counting down. A few miles from some small town that might have DEF, the gage, while I was watching intently, went from full to almost zero in the course of 5 or 6 seconds. OMG!

Finally, got to station and paid a king's ransom for 2 jugs. After a quarter or so, the DEF tank overflowed. Great, now what?

Started it up and everything was fine the rest of the trip and has been since.

Until yesterday. A week ago the DEF gage was getting down to just over a quarter. I got 2 jugs from Walmart and they both went in. Gage was full. Made a number of trips no problems. Yesterday, I'm pulling the trailer from Youngstown, OH down towards Cincinnati. And it starts with the countdown. I go to check the gage and it's not the dash where it should be.

I figured since the gages went back to default, i must have gotten some OTA update. When it got down to about 10 miles to go, we stopped at a rest stop. Came back out and it has been fine since. I'm betting the OTA update reset something and it needs a couple starts to figure the correct level. Can't say if that was our problem in the Yukon.

 

23+ yes, but OP has 2017. 2017-19 at the least would not show percentage on the gauge but 1/4 tank increments. At least thats how the gauge read on mine. I stuck with the iDash to know for sure.

 

Now, that's just wrong, making your pregnant wife pull the trailer when you could have hooked it up to the truck!
SHAME ON YOU!!!

 

Why would you let the truck get OTA updates when it wants to?

 

Sorry for the delayed update. After spending 2 hours at the dealership we got back on the road & arrived home after 9pm. That made for a long day having left yesterday morning around 8:30am & passing thru a time zone. We arrived home with no further issues so for that I’m thankful. I had never heard the DEF tank should be completely filled when low. In 7 years + of owning my truck (2017 F350) I have always added a jug to bring it close/closer to full but not necessarily completely full. No issues until now. I’m going to need to learn how to fill it without letting it overflow - might be messy! Thanks all for your input! Nice to know there’s someone to talk to when you’re feeling alone.

 

Glad it work out. Suxs having delays like that on travel days.

My 16 I just fill the DEF tank occasionaly with 2.5g jug and before long trips pulling the 5th wheel I'll top off completely with 2 2.5g jugs and pour any leftover in after the long trip. Seems almost impossible not to spill some DEF when topping off. Nothing some water and rag doesn't clean up. 😉

 

The way to fill without spilling is to fill at the truck stop DEF pump.
There are also DEF pumps at some other fuel stops.
But, as I stated, I do not think that was the issue you had.

 

It's a bit tricky to do, but I've gotten fairly good at it. I just listen for it to start to 'gurgle' similar to how the fuel does when it's close to full. As soon as I hear that it's time to stop, because a second or two later and it's coming back out the fill hole. It's much quieter than the fuel 'gurgle' because it's a smaller hole, but you can hear it just before it overflows.

 

It may or may not have been. The video I posted above details why it happens. I used to fill up with the jugs to begin with but saw the video and changed to truck stops or Bucees/Racetrack fuel depots.

 

Doc said exercise was good for pregnancy.

 

I recently had the same DEF warning 50 miles till reduced power fault while towing my 5th wheel and it ended up being one Battery was bad..
I didn’t know what it was at the time but I drove 100 miles home And no countdown happened but the error was still there.
Threw a couple other codes as well.
All this happened after I left my lights on at camp and needed a jump, apparently the batteries were already going bad

disconect both batteries and test them before going to a shop to diagnose further. I

 

This morning going down the interstate pulling a 5th wheel, mine popped up the warning message and started the countdown, 50 miles to the 50 mph limited speed, but then about 15-20 seconds later all disappeared and had no more warnings and no issues all day.

 

EPA really messed these trucks up.