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Discussion Starter #1
I picked up my 2014 F350 from the dealer yesterday after they serviced it. It sat outside at the dealer for 5 days in temps from 10-20 below zero. Driving home the low DEF light came on so I stopped and got a jug of DEF(2.5 gallons I think) and added it. 10 miles later a message comes up "empty Def tank limp mode in 99 miles" Called dealer this morning and he says DEF is frozen, the DEF heater will take care of it. Problem is I have 60 miles before it goes into limp mode and it hasn't thawed yet.

Do I let the truck idle for a couple hours in the parking lot at work, or wait until I get home and put a heater under the truck? I don't want to let it idle if that will cut down on how far I can go before it goes into limp mode.
 

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I don't have any direct experience using DEF on my older Powerstrokes but here are some facts about DEF that might help you make a decision:

Q. What is Diesel Exhaust Fluid (DEF)?
A. DEF is the reactant necessary for the functionality of the SCR system. It is a carefully blended
aqueous urea solution of 32.5% high purity urea and 67.5% deionized water.
Q. What is the freeze point of DEF?
A. A 32.5% solution of DEF will begin to crystallize and freeze at 12 deg F (-11 deg C). At 32.5%, both
the urea and water will freeze at the same rate, ensuring that as it thaws, the fluid does not become
diluted, or over concentrated. The freezing and unthawing of DEF will not cause degradation of the
product.
Q. How do I keep the DEF from freezing? What happens if the DEF freezes
in the tank on the vehicle?

A. During vehicle operation, SCR systems are designed to provide heating for the DEF tank and supply
lines. If DEF freezes when the vehicle is shut down, start up and normal operation of the vehicle will not
be inhibited. The SCR heating system is designed to quickly return the DEF to liquid form and the
operation of the vehicle will not be impacted. The freezing and unthawing of DEF will not cause
degradation of the product.
Q. Can an anti-gelling or freeze point improver be added to the DEF to
prevent it from freezing?

A. No. While an additive could improve freeze point of the mixture, the 32.5% solution is very specific to
providing NOx reducing properties. Any further blending or adjusting of the DEF mixture will impede its
ability to perform correctly and may cause damage to the SCR components. Additives of any type are not
approved for use in DEF today. If the ISO standards should change to allow antifreeze additives,
Cummins Filtration will ensure our product continues to meet ISO requirements.

Taken from a Cummins website:
https://www.cumminsfiltration.com/sites/default/files/MB10033.pdf
 

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Unless the DEF tank heater is bad, it should thaw the DEF before it goes into limp mode.
 

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Discussion Starter #4
Thanks for the help guys. I drove 30 minutes to work today and the truck has been running for 2 hours. Either the tank heater is bad or the tank level sensor is wacked. Either way I think the dealer is yanking my chain and I will be visiting him tonight. 5,000 mile left on warranty so this has to happen soon!
 

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The DEF gauge and warning is wacky on these.. I've have numours times it told me it had 500 miles before shutting down. Added fluid and took a long while to go out. Maybe it's your case. You have to fill it up to the top. Adding 2 1/2 gallons when the tank is low isn't going to do it.
 

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Discussion Starter #6
Back to the dealer last night and after a thorough inspection, DEF was not frozen, pump was pumping at 75PSI, sensor working, tank was 65% full, it was just taking it sweet time resetting. Tech said by the time you get home it will have reset. By the time the service writer got the truck pulled around front for me the light was off and all is well. Took over 24 hours to reset. Just an FYI if someone else runs into this issue.

One more related question, when you plug the truck into the block heater does this also run the DEF tank heater? I forgot to ask the dealer that last night, but it sure seems like it would make sense since DEF freezes at 12 degrees.

Thanks again for the help gents!!
 

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No, the DEF tank is not associated with the block heater. The block heater only warms the engine coolant.
 

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Back to the dealer last night and after a thorough inspection, DEF was not frozen, pump was pumping at 75PSI, sensor working, tank was 65% full, it was just taking it sweet time resetting. Tech said by the time you get home it will have reset. By the time the service writer got the truck pulled around front for me the light was off and all is well. Took over 24 hours to reset. Just an FYI if someone else runs into this issue.

One more related question, when you plug the truck into the block heater does this also run the DEF tank heater? I forgot to ask the dealer that last night, but it sure seems like it would make sense since DEF freezes at 12 degrees.

Thanks again for the help gents!!
Happens to me as well. takes its sweet time .. always at the worst times...like during a cross usa trip or having to do a important work related trip.
 

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Discussion Starter #10
Happens to me as well. takes its sweet time .. always at the worst times...like during a cross usa trip or having to do a important work related trip.
Have you ever hit zero miles and gone into limp mode because of it? That was my only fear. Going 50 mph on the freeway where the slow guy is going 70 mph would not be fun.
 

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Have you ever hit zero miles and gone into limp mode because of it? That was my only fear. Going 50 mph on the freeway where the slow guy is going 70 mph would not be fun.
No...someone said to disconnect the battery and that set it but it didn't do it instantly.. Ford dealer can reset it ..try to get an appointment to do it the day before you have a work trip planned.. I should can the dealer...

Anyway.. I learned to fill it and keep it filled between important trips. Don't let it get low so the light comes on. Then it can take it's sweet time to know it's full again and reset to full.

I've had the issue in the summer or winter don't matter. But in 80k miles only a few times or so..maybe 4? not sure.

Somehow the glitch for this is not steady enough to figure out .
 

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My 2012 went into a false low level mode once (mileage count down). Under some situations, 4 restarts will reset the DEF measurements--mine did. I wait until I get 2 or 3 fill-ups past the half low point, then dump a jug in. Doesn't seem to want to take a whole jug immediately after the half alarm. Not letting it get down lower has seemed to eliminate those mileage warnings.
 
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