I am really getting tired of having. 80% DEF and getting warning messages when I tow.
any way to change the warnings?

 

You can't change the warnings, but you can solve the problem. I have fought Ford over this issue and they will not do anything about it. The best part is once the warnings start, they won't stop until you fill the DEF tank. I think they are overdosing the DEF. When I inspected my exhaust just downstream of the injector, I found golf ball size chunks of crystalized DEF. It is injecting so much that the exhaust can't vaporize it.

 

You are getting a low def warning at 80% if I understand your question.
I have gone down to 50 with no warnings
I think I use more than it should, but that's an opinion.
but on ford owner page I got a red indication
Not in ford pass or in truck
Now I cheat and carry 2 gallons in tool box
And top off at 85%
I do more combined city miles
but on long highway drives the def seems to tick down very slow compared to the combined miles.
it's odd for you in tow mode. For truck to see 80 as a low condition imo

 

What he is saying, is. While towing and you start from a full tank of DEF, at the 80% full mark the truck will start giving you a refill the DEF soon message. Now the bad part about this is once this starts it will not stop until you refill the tank. It continues to count down. At this point it is only counting miles. It doesn't matter what is in the tank. The truck is ignoring the actual tank level. Then the messages start giving you a distance to empty. At 50 miles to empty the computer will start reducing the amount in the tank so that at 0 miles to empty the gauge will now read 0% DEF in the tank. Also at 0 miles to empty the truck will go into a 50mph limit. If you shut the truck off and restart your gauge will read the correct amount again, but as you drive at 50mph the computer will drive the tank level down again. Restart the truck and it will read correct again, but still limited to 50mph. My truck would read as much as 50% DEF level, but still limit to 50mph. It will not reset until you refill the DEF tank. It's all software driven. Maybe they will straighten it out one day.

Now my truck reads 100% DEF with the est distance of 64,999 miles.

 

Get into the dealer, something isnt right, unless this is a 2023 only "feature". On my 2024, Ive run mine down to 50% and do not get any warnings.

 

50% when empty or not towing will not set it into this condition. Usually towing heavy is when it happens. In my experience anyway

 

Have you had any software updates completed on your truck? May be worth getting with @ZooDad and renting his cable. I have been down to 60% with no warnings. I would try updates if possible.

 

Its so strange that theres not a standard warning level. Mine is very consistent. A warning pops up and the icon flashes when I have an estimated 500 miles remaining on the DEF tank. That gives me plenty of time to swing by the local 7-11 or QuikTrip and fill er up!

 

That's the thing - when towing, these rigs automatically adjust the DTE (distance to empty) for both fuel and DEF, to the VERY conservative side. Meaning your DEF DTE drops from say 2500 miles at full to 1000 miles or less. Depending on what that number is, you could get the '500 miles to empty DEF' warning as high as 80% as OP has seen. And it won't go away until you refill the tank.

I remember seeing an older thread on this a while back, and that's basically what happens, and there isn't really a way to tell the computer otherwise.

 

Has anyone figured out how to change when it alerts? It isn't broken, there isn't an issue. I'm referring to the standard miles to empty when it constantly flags and says 499 till empty. I'd rather have it be at like 100 miles

 

Has anyone figured out how to keep the software from bricking your truck like that and limiting you to 50mph? That is downright dangerous to be limited to that.

 

What I find aggravating is how it doesn't adjust with the fuel dte. For example I filled my truck with fuel and def towing our 20k rv. Next fuel fill I didn't add def. In my 21 I could go every other fuel fill filling with def with no warnings. In the 26 not far into second tank of fuel def warnings start up. 500 dte. Fuel reads 300 dte. How stupid is that? There has to be way to sync those right? If the truck can adjust on the fly to fuel usage surely it can send def reminders to sync with low fuel at that point?

 

I've fought this same thing since I bought my '25. The DEF warning comes on when the computer estimates that you will use the remaining DEF within 500 miles. This is based on the current rate of usage. Since Ford overdoes the DEF injection, it can be with 80% of the tank remaining. That is when mine typically comes on. Been to multiple dealers and they all say it's working as designed. The heavier the load you are pulling, the harder you push the accelerator, the faster you use DEF and the sooner the computer starts complaining. It's annoying to have the notifications keep popping up, but mine won't threaten a shut down until the gauge actually shows 1/4 tank. When I run cows across the country, I fill the empty DEF tank every other fill up. I truly burn almost 2 gallons of DEF per tank of fuel. Having said all that, notifications at 80% is normal for a truck that is working hard and without removing the system, there's not thing you can do about it. (2025 F450 HO)

 

That's wild. I routinely let mine get to 22% (with no warnings). That way I know it will hold 5 gallons of DEF.