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I spent some time and went through threads about the erroneous DEF warning, count-downs ETC. I have a 2016 Dually. I got the warning, 500 Miles... I added one container full of DEF and the message reset.
2 days later it came in again, it has been there at each start up and is faithfully counting down, currently at 336 miles left.
So I am wondering what the best course of action is.
Should I stare down the barrel and dare the truck to put me in a 50 MPH clamp down?
Top the reservoir off?
Dunno!!
Fill it completely full. I have had the same thing happen when I didn’t fill the Def completely. Others will tell you they had no problem with partial fills but I have had to do a complete fill to get the message to reset.
I always do full fill even if it doesn't take a full container of DEF to fill the tank. Try filling it and see if it resets.
Also, get one of the Ford DEF nozzles PM-27-N. It will fit most DEF containers ok. It will stop filling the DEF tank when it is full and won't overflow like the nozzles that come with the DEF. It also fits tight into the DEF fill tube. You can get one usually for around $10 or less. I wash mine with clean water and then store it for use again when needed.
dare the truck and hope it fixes itself. Next time as suggested by Larry, run it down to <200 miles to empty then do the complete refill.
My 2013 has always been completed this way and in now going on 7 years has been fine. No work on any of the SCR components.
Personally - I've been there are dared the truck to do it. Had the countdown on multiple starts, DEF tank was absolutely full. Somewhere around the 30 miles to limit mark the truck decided to finally fix itself. Didn't have a lot of options at the time (past business hours in rural NE and KS). Not a comfortable feeling.
I typically wait till I get down to about 200 miles then put in 2 of the 2.5 gallon containers. Seems to work well (I have a 2019 so tank size may be different).
When I get the 500 miles warning, I fill it up all the way. It does take 2 containers but does not use all of the second one. I have filled it up completely before the warning and never had a problem. I now wait until I get the message and make sure to completely fill it with the Ford DEF nozzle.