I got back from camping with the fifth wheel last Sunday. I got the 500 mile range warning on the DEF while dropping off the trailer at storage, so I bought the BlueDEF 2.5 gallon container that same day and poured it all into the truck (in the correct tank). Today, two days later I got the 500 mile DEF warning again.

What gives?

 

I could be wrong, but to reset the countdown, you have to fill the DEF tank completely.

 

Need to fill it completely up to do a reset.

 

Really? This is odd, because I've only ever filled this thing when I got the warning, and it was always the same amount of DEF. Probably done it 10 times now without seeing this happen.

I'll get more DEF and try filling it completely, I suppose.

Thanks.

 

I'd run it down to closer to 200 miles till empty. Then it will fit almost the 5 gallons.

 

Read this post. Evidently, you need to wait until the DEF tank is lower before adding more DEF. After an hour or so of driving, mine cleared the error message. https://www.ford-trucks.com/forums/1...def-issue.html

 

Yup, you've never filled your tank above 1/2 full so the way the tank level sensors work is confusing. There are only 3 level indicators, full, 1/2, and 1/10 I think. The 500 mile estimation is based on the presumed 5000 mile capacity of the tank.

Filling the tank completely is not easy when I try it. If you run it down to 100 miles left you can get 5 gal in there but the last gallon takes patience and it helps if the truck is parked facing up a slight hill.

 

Almost..... Actually the first level indicator rod is at the 1/2 tank mark.

Here's pretty much what happened to the OP:

Most likely it was filled to right at the halfway point. The PCM can't see anything above half a tank, so the miles to empty "reset" thinking it's a full tank. After only a few miles of driving it drops below half tank, and the PCM freaks out thinking it's sipping DEF like a beer chugging sailor on shore for the first time in 6 months. So the miles to empty is now adjusted for very rapid use and the countdown shows 500 miles to empty even with just below half a tank.

The DEF system is very simple..... and hence not terribly smart. Follow what the owner's manual tells you and most likely you'll never have a problem. But if the tank is continuously topped off, or if run nearly empty and only filled halfway, there's going to be times when the system becomes confused and you get errors like these popping up.

Always run the DEF down until the driver information display tells you to refill (500 miles or less to empty), and then fill the tank completely. It's best to use the Ford fill tube to get it full without overfilling or spilling all over your paint.

 

My 2011 I kept full most of the time topping off often and never had an issue. I only have 6k miles on my 2015. I saw the 1/2 full message and topped it off COMPLETELY using the ford filler tube. As soon as I did that it reset. I mean within seconds of starting the truck...

I do agree that when you fill it, you need to fill it ALL the way. When you see the 500 miles to empty, you need more than 2.5 gals. Seeing as when I hit the 1/2 full mark it took slightly more than 2.5 gals. Unfortunately where I live now, there are no DEF pumps as I usually like to use them to top off the tank...

I did notice the dealer at oil change topped off the DEF tank. I am careful not to spill any and if I do, I clean it up... They didn't... I had white crusty DEF all over the inside of the fuel filler door area. At least they tried to do a good thing for me.