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DEF System Fault

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Old Oct 22, 2017 | 04:00 PM
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DEF System Fault

2012 F250 6.7L with 99k miles has DEF system fault. DEF fluid is full. Using Motorcraft specified fluid. What cause, what is fix?
 
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Old Oct 22, 2017 | 04:11 PM
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are you saying it is full and you have the fault.


Was this prior to a fill up? How often do you fill it? Do you let it run down to around 200 miles to empty and then fill up?
 
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Old Oct 22, 2017 | 04:19 PM
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Yes. DEF system fault appeared. I had no low DEF warning. I topped off DEF and it took about 1 gallon. Started truck and DEF system fault still appeared.
 
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Old Oct 22, 2017 | 05:34 PM
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There is part of your problem. Frequent unnecessary filling of the DEF gets it confused.


Let it run down till you get a warning of about 200 to empty, then do a complete fill. It will work better.


You may have to take it in for a reset, but drive it for a few days and see what happens.
 
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Old Oct 22, 2017 | 06:23 PM
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Thats what I did, i didnt fill it until a little after I got the 500 mile DEF low fluid warning. It was fibe for another few weeks and then all of a sudden the DEF system fault occured today.
 
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Old Oct 22, 2017 | 06:50 PM
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My issue is different, the last two times I have gotten the 500 mile to empty. I run it down to where it reads 200 miles plus or minus a hair then fill it up. But, it doesn't even take a full 2 1/2 gallon bottle before it starts overflowing.

It was my understanding that the DEF capacity was closer to 5 gallon total.
 
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Old Oct 22, 2017 | 06:59 PM
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@<200 to empty mine will just about take 5 gallons.


So, something is wrong if it is calling for def and you are getting the count down and it is not taking but a gallon.
 
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Old Oct 22, 2017 | 07:04 PM
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Thanks for your help. I am going to take it to the dealer where I bought it and see what they say.
 
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Old Oct 22, 2017 | 08:17 PM
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Did you pull any OBDII codes? That might give you and indication of the problem.

From the 2015 Diesel Owner's Supplement Manual...

Selective catalytic reduction systems are sensitive to contamination of the Diesel Exhaust Fluid (DEF). USE ONLY API or ISO 22241 CERTIFIED DIESEL EXHAUST FLUID (DEF). If the selective catalytic reduction system becomes contaminated or inoperative, the Diesel Exhaust Fluid (DEF) light will illuminate and exhaust fluid system fault messages will appear in the information display.

I would first try pumping the DEF out of the tank and refill with fresh DEF. If still a fault, take to a dealer. It may require a few drive cycles to clear the fault light.

you can get a pump like this at Wal Mart or Harbor Freight to pump the DEF out of the tank...

https://www.walmart.com/ip/Custom-Ac...-Pump/16767856
 
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Old Oct 29, 2017 | 10:12 PM
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Joe-
Read your initial post with much interest. I have a 2012 6.7 that I just purchased to pull my fiver. Got my first DEF warning at 500 miles till empty. At 400 miles till empty I bought a carton of BluDef. It only held slightly over 2 gallons of the 2.5 gal in the box. Warning went away about a day later so I guess all is well.

What I wonder about is why I have a 5 gallon def tank (or so I am told) and I got a low def warning when the tank is still half full?

Hope you are getting your issue straight. Keep us posted.
 
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Old Oct 30, 2017 | 05:05 AM
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don't till it so fast. let it get down to around 200 to empty. It was estimating based upon your rate of consumption.
 
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Old Oct 30, 2017 | 02:36 PM
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Originally Posted by Dawgfever
Joe-
Read your initial post with much interest. I have a 2012 6.7 that I just purchased to pull my fiver. Got my first DEF warning at 500 miles till empty. At 400 miles till empty I bought a carton of BluDef. It only held slightly over 2 gallons of the 2.5 gal in the box. Warning went away about a day later so I guess all is well.

What I wonder about is why I have a 5 gallon def tank (or so I am told) and I got a low def warning when the tank is still half full?

Hope you are getting your issue straight. Keep us posted.
What he said, plus the previous owner may have filled it up at an odd time and the sensors are confused. Meaning, it may have had a lot more in there than it thought. You can probably drain the entire tank, reset the sensors, refill, and be back on track.
 
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Old Nov 3, 2017 | 09:36 AM
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Joe Lewis - the boxer or that's what you were named? Anyway, did you find out what was wrong? What did the dealer say?
 
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Old Nov 3, 2017 | 01:49 PM
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I had the fault come one and it only took 1 1/2 gallons. Wouldn't go off for many many restarts.. after a total filling. Is there a way to reset it our selves? with out the dealer?
 
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