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Discussion Starter #1
I've seen lots of posts on here where DEF gauges are reading too low...consensus seems to be it froze and didn't read a fill, or never dropped level and usually related to very cold weather. I can understand the logic there.

My DEF tank is about 1/4 full, and I always keep it between 1/4 and 1/2. Never had a problem with DEF usage (minimal) or the guage and had the truck almost 2 years now. Always parked outside and seen lots of cold weather. Once last year in a stretch of 2-3 days of extreme (-20 to -30 C) cold, I got the P20E9 Code. I cleared the code with a code reader and it never came back. I figured the DEF had froze.

This morning (-16 C), I get in the truck and the DEF gauge reads 100% full. How could that be? If it froze, I could see it now going down with time, or not going up if I filled it, but how could 1/4 tank of DEF freezing read 100% on the gauge?

Also, something odd I noticed this monring...when I turn the KEY to 'accessory' the check engine light stays on. It's not present when I start the truck. Not sure if that's new or not, never really noticed it before. Does yours do that?
 

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I've seen lots of posts on here where DEF gauges are reading too low...consensus seems to be it froze and didn't read a fill, or never dropped level and usually related to very cold weather. I can understand the logic there.

The CEL is normal to be on in the Acc. Position, it's letting you know that it's functioning. Cold Weather and DEF readings have always been issues.
My DEF tank is about 1/4 full, and I always keep it between 1/4 and 1/2. Never had a problem with DEF usage (minimal) or the guage and had the truck almost 2 years now. Always parked outside and seen lots of cold weather. Once last year in a stretch of 2-3 days of extreme (-20 to -30 C) cold, I got the P20E9 Code. I cleared the code with a code reader and it never came back. I figured the DEF had froze.

This morning (-16 C), I get in the truck and the DEF gauge reads 100% full. How could that be? If it froze, I could see it now going down with time, or not going up if I filled it, but how could 1/4 tank of DEF freezing read 100% on the gauge?

Also, something odd I noticed this monring...when I turn the KEY to 'accessory' the check engine light stays on. It's not present when I start the truck. Not sure if that's new or not, never really noticed it before. Does yours do that?
The CEL will stay on when in the Acc position. Its letting you know that it is working. DEF readings and cold weather = erratic readings ,who knows what the heck the computer is doing!
 

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Discussion Starter #3
Thanks RAM1, good to know about the CEL in acc mode. I figure the DEF is just frozen, just struggling to undertand why mine would jump to full and stay there when the average 'frozen DEF' experience is not that
 

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This will read silly but remember, water expands when frozen. How much is for your gauge to determine.

Seriously. Wait for a thaw and then make a judgment.
 

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Discussion Starter #7
Well, mystery solved. Apparently the wife filled it. :rolleyes: To the top. :mad:

Since I bought the truck, I've made sure to only fill it at the busy truck stop on the highway, at least she went there...but I've also been sure to keep the DEF between 1/4 and 3/4 always, she's been there when I've pulled out the manual, referenced the section that says 'if your DEF is X full you can put in Y gallons of DEF' then watched me pull out the phone and use the internet to convert gallons to litres and meticulously put in the required amount so as to NOT overfill the DEF. We get cold winters here, already had the DEF freeze once last winter and got the dreaded "truck won't restart in 320 KMS" message.

So....now I have a DEF tank filled to the top in the dead of winter. I have read cautions to not do that, as it could freeze/crack, especially up the neck of the DEF tank....should I be concerned enough to siphen some out now? It was -16 Celcius here this morning

I'm worried about it freezing and also a bit worried about it 'going bad'. Based on my driving, I would estimate that full tank of DEF will probably last me a year or more. I've had the truck for 19 months and ~32,000kms. It had 3/4 tank of DEF when I brought it home, and have only put about 14 Litres in it over that entire time. What happens to DEF when it 'goes bad'?
 

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If your worried (I would be also based on your location) just siphon a gallon or so out. I wouldn't even worry about saving it as it could get contaminated. As DEF degrades over time it becomes less effective.
 

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What happens to DEF when it 'goes bad'?
When you say she filled it to the top, how much did she put in?
I think FCA puts the overfill warning in the manual because you can overfill it easier when using jugs verses filling up at the pump.
Don't worry about the DEF going bad, under most temperature conditions, it will be good for over a year in the tank.
I will question the amount of DEF you stated you have used, loosely calculated by the number of kilometers, the truck should have gone through somewhere around 50 liters.
 

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Discussion Starter #10
thanks for the input guys...maybe I will siphen some out.

Wife said she put in about 18 litres, which makes sense as it was ~1/4 full at the time and it's full now.


I will question the amount of DEF you stated you have used, loosely calculated by the number of kilometers, the truck should have gone through somewhere around 50 liters.
Well, that's all the DEF I've used in 32,000 KMS, I'd guess around 36 L. I thought that didn't seem like much, but I thought DEF usage varied based on drive type? Mostly highway for the truck, never seen an active regen message on the EVIC
 

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Well, that's all the DEF I've used in 32,000 KMS, I'd guess around 36 L. I thought that didn't seem like much, but I thought DEF usage varied based on drive type? Mostly highway for the truck, never seen an active regen message on the EVIC
DEF usage has nothing to do with regeneration cycles. Regeneration happens in the DPF, DEF is injected in the SCR which is downstream of the DPF.
Maybe I was reading it wrong but using 14 liters(3.7 gallons) of DEF in 32000 kms(19880 miles) is way low and surprising you haven't thrown a code if that is the case. DEF usage should be approximately 2% of the amount of diesel fuel burned.
Just for reference, DEF doesn't start to freeze until below 12°F(-11°C).
 

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Discussion Starter #12
huh, good to know Crash. I really thought DEF usage was dependant on driving conditions like the regen business. Oh well, I'm not too concerned about low DEF usage. Only had one code, the P20E9 last winter, pretty sure it was due to frozen DEF. The countdown message cleared on it's own, I cleared the CEL with code reader and it never came back. I could swear I've read posts on here about DEF usage implying a wide range of usage rates...some guys burining through DEF like crazy, others like me seem to use almost none. Is the lack of DEF usage damaging to any part of the truck, or just the environment?
 

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Well, mystery solved. Apparently the wife filled it. :rolleyes: To the top. :mad:

Since I bought the truck, I've made sure to only fill it at the busy truck stop on the highway, at least she went there...but I've also been sure to keep the DEF between 1/4 and 3/4 always, she's been there when I've pulled out the manual, referenced the section that says 'if your DEF is X full you can put in Y gallons of DEF' then watched me pull out the phone and use the internet to convert gallons to litres and meticulously put in the required amount so as to NOT overfill the DEF. We get cold winters here, already had the DEF freeze once last winter and got the dreaded "truck won't restart in 320 KMS" message.

So....now I have a DEF tank filled to the top in the dead of winter. I have read cautions to not do that, as it could freeze/crack, especially up the neck of the DEF tank....should I be concerned enough to siphen some out now? It was -16 Celcius here this morning

I'm worried about it freezing and also a bit worried about it 'going bad'. Based on my driving, I would estimate that full tank of DEF will probably last me a year or more. I've had the truck for 19 months and ~32,000kms. It had 3/4 tank of DEF when I brought it home, and have only put about 14 Litres in it over that entire time. What happens to DEF when it 'goes bad'?
Chill out. DEF doesn't go bad in cold weather. I've filled mine until the pump clicks off at -25F and my tank is fine.
 
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