2014 F250 Diesel I got the msg saying 50 miles until speed limited to 50 mph. None of the earlier warnings re adding def. check def on computer and it said it was ok. I even added def and it only took a small amount until it overflowed. It was more than 1/2 full. The error message did not reset. I drove it around for several miles and it still would not reset.
Having it services as we speak, and the tech is still having difficulty running down the cause. He has done a regen,and reset the computer and etc and still has not resolved the issue..
Any thoughts or suggestions?

 

My personal opinion is the wacky system they use to determine how full or low the DEF tank is. I've gotten random messages about being low shortly after topping off the DEF, only to have them later disappear and not come back.

I don't know if there's a way to pull and clean the rods in the tank, or just unplug them and let them reset, or what the answer is. Doing a manual regen while the tank is full and the only symptom is a DEF message tells me the Ford tech is just guessing and has no clue what he's doing.

Moving to a different tech or dealer might be a good move.

 

Do you keep your DEF topped off or let it run nearly out before filling up?

 

I'm thinking there's a recommendation coming from that question - can you give us the comments on both sides of the question?

 

Chuck, you're as new to diesels as I am. Based on a couple threads I've read I'm keeping my DEF level at half or higher. At the very least, it gives me a huge buffer from ever going into reduced power mode due to low DEF. There do seem to be some DEF tank sensor issues. Will keeping it above half prevent that? I don't know, but keeping it topped off is easy enough.

 

Quite the opposite in fact.

DEF freezes, so you can't use a floating assembly to measure the continuous amount in the tank. However, DEF does conduct electricity.

So the setup is designed with 4 rods in the tank. A ground rod, and 3 level measuring rods. The first rod is near half tank.

The system is also setup with a mileage countdown. When the system "sees" a refill event, the mileage countdown is reset. That mileage countdown is adjusted as the DEF level falls below each of the 3 level indicating rods.

Now let's say you keep the tank topped off, what happens to the mileage countdown? Well, the mileage countdown will keep going down. Since the system never sees a refill event, eventually the countdown will run all the way down, even with a full tank.

This doesn't happen all the time, but it's often enough that we continue to see threads like this pop up regularly. I'm not saying that's what the OP has done in this particular case, but these discussions crop up often regardless.

The owner's manual specifically states not to refill until you're below the 500 miles to empty countdown. This helps ensure that a refill event is seen by the system and everything resets properly. Not following the owner's manual increases the chances of having DEF countdown errors.

 

Thank you for the description of how the DEF tank level is determined. That is good info.

I just reviewed the online 2017 owner's manual and I can't find anything about a requirement to wait until below 500 miles to refill. The online version is hard to search so maybe I just didn't find the right area. My gauge accurately detected my refill even though it was only half full before the refill.

 

I check my DEF level often. When it drops below 1/2, I drive for a couple of hundred miles more, and then pour in a 2.5gal Jug. I started doing this back in 2010 when I purchased my 2011 6.7, and have continued to do it this way with my 2016. I have had the Premature Countdown only happen once. Filling the DEF Tank cleared the Countdown. I think that the 2017 F Series has a Dash mounted Gauge like Ram Does

 

Same here.

 

On the previous body trucks, the diesel supplement has a chart. Where exhaust fluid level is OK or Under 1/2 Full, the action listed on the chart is to drive normally and to take no action at that time.

Only when the exhaust fluid Range 500mi or less warning comes on, then does the chart specifically state to refill exhaust fluid.

The 2017 manual doesn't have that chart.

 

Sounds like I can fill up at any time then. Thanks for the update.

 

I think there is quite a bit of difference between the 2017 and at least my 2013. Not sure if Ford made improvements in the 2014 - 2016s, for those folks I sure hope so. Jim, I believe your truck has a DEF gauge? What I wouldn't do for a gauge. I have no idea what was running through the heads of the architects of the DEF system when they thought "hey I've got an idea, let's not put a gauge in lets just send them a message when it's almost empty". Hopefully they were fired.

 

Chuck, I do indeed have a DEF gauge. The movement of the gauge and the smell of burnt cookies is how I know my truck has been through a regen cycle. Otherwise, I don't notice any difference.

 

Since the original post mentions that the info center says DEF level ok, and since he said it is physically full, I think we can rule out the level sensors, or filling frequency as the issue for this one. There is either an issue with the pressure sensor, injector, heater or pump - in my opinion. I would lean more toward the pump or pressure sensor, since it suddenly started giving a countdown. It appears to either not be injecting DEF, or not thinking it is anyway.

 

i had the same exact problem as the OP, def fluid fine, but none the less a fault in the fluid system.

I was on vacation pulling my tt when the fault arose. Short story is the def nozzle was partially plugged limiting how much def could be injected. There is a service procedure on IDS that allows the dealer to "clean the def nozzle" basically forcing a bunch of flow to clear the obstruction.

I cleared the code which allowed me to get to my destination (kept my pace a little slower). Upon arriving at niagra falls, West Kerr ford gave me a loaner, performed the procedure and we were on our way. Great dealer to work with on the road.

Basically though, the NOx sensor did not see enough def being dispensed to keep levels in check and gave the fault.