Interesting experience with DEF

[random_james]

So, about 150 miles prior to arriving at Williams, AZ to visit the Grand Canyon, we filled our DEF tank. Drove to Williams, showed nearly full on DEF. Camped for several nights, started the rig, and it read completely empty on the DEF, and gave us the warning on the dash (Empty DEF, 200 miles until 5mph limited mode!). Started worrying we had a leak. I always carry an extra box of DEF with us, so I used that to add 2.5 gallons. No leaks observed, but DEF was still reading empty, with the warning message. At this point I'm thinking that there's a bad/disconnected sensor, or a computer problem. Start calling nearby Dodge/RAM dealers to see if anyone can get us in, finally find one about 2 hours out of our route down in Prescott that isn't a week out for service, and drive down. After waiting there for about 3 hours, they fill the DEF tank (took about 7.5 gallons!), clear the codes (only code was "Empty DEF!"), and everything is working again.

Several days of driving since, and everything is working fine.

Only thing I can think of is that maybe some idiot came and siphoned our DEF tank empty when we were away from our camp site, and the 2.5 gallons weren't enough to register on the sensor. I'll be adding a locking cover for the DEF fill.

Anyone seen anything like this before? Any other ideas as to what could have happened?

Oh, and if some a**hole did siphon our DEF, I *really* hope that they thought it was fuel, and added it to their gas or diesel tank!

[aeblank]

Wow, that's weird. Your capacity is large, but gosh, a jug should register... I'd be asking around to find out the amount to add to make it go away. Seems to me if you want to go empty to 2.5 gal for the life of the vehicle, you should be "allowed".

[formerFR]

theft 'could' be... let's use some math.... your def tank holds 9 gallons, I assume the alert would happen with 1 to 1 1/2 gallons.

if you filled at 150miles prior, you should probably have had at least 8 gallons when you parked. when you found the alert, you would have been left with 1 1/2 gallons OR LESS. when you drove two hours to the shop, you would have been down to very little, less than a gallon I presume.
the shop added 7 1/2 gallons, I assume you mean THREE containers, which would have brought you up to 8 to 8 1/2 gallons, or close to full, technically...

I believe, also, that adding def when you are not cranked may not register on the dash indicator until you've traveling a while. Some cars do this with fueling, my wife's car won't register being full if she fuels while the engine is running, until several miles down the road. weird.

so maybe theft is the answer, as it seems very little other reasoning could bring you a loss of so much def, with so few miles, if no leak was found.

I also had a situation with mine where the DEF indicator alerted me to low DEF, one bar, but I knew I had plenty. The problem? The Freightliner dash indicator was not registering correctly, as the tank indicator itself showed almost 3/4 full.

After talking with FL, they had me go thru several steps with the dash computer and 'reset' something, can't remember exactly what it was, but it worked. No problem since.

I've also heard or read that DEF sitting in a tank for long periods can 'dry up', as indicated later by the dry flaky white stuff that happens when you spill some, and create issues with how the computer reads the def level at the tank. I don't 'know' if that's really possible, but it certainly seems plausible.