DEF guage/issues

[bartbill]

Drove from Sand Point Idaho to Brigham City, Utah and the needle on the DEF gauge never moved (2015 Ram, 6.7)

So I stopped in the Dodge dealer and talked to the service department about it. He was pretty familiar with issues about the computer throwing codes about DEF problems - 2 in the last week. Sometimes the computer threatens to shut down in 150 miles but if you keep driving it the warning just goes away.

So I bought a jug of DEF and it took about all of it - so I know it is using DEF.

Anyone hearing of this issue? Bad gauge software problem? Defective guage?

Any ideas?

 

[drittal]

At 3/4 on the gauge I can add a 2.5g jug.

Because it can freeze it doesn't have the traditional float sending unit for the gauge.


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[Ratket]

The Deff can crystallize as well if it dries- This could be causing a read out issue.

 

[Tach_tech]

There's issues with the DEF systems, but it's usually related to the SCR, the pumps, and the module, which is pretty much the entire system. However I'm going to gander a guess you may not have an actual problem.

The thing with DEF is it's not like fuel, it's not constantly being used. It's only injected into the exhaust when required. We've had people come in with the same concern but once it's explained to them how it works, it makes sense.

So basically when the NOx sensor determines that the NOx levels reach a certain point, DEF is then injected to control the NOx levels. If NOx levels are ok then no DEF is injected. If you're just cruising down the highway not towing or anything you will use very little DEF if any. Now if you're towing some heavy ass trailer, you're going to use a lot more DEF, since NOx will be higher, you'll also be using a lot more fuel.

As for adding DEF to the tank even when it reads full. I'd have to find the star case about it, but I believe it's due to the fact there are actually 2 different tank sizes for the HD trucks. Yet the level sensor is calibrated to read full at the same level for both tanks. It doesn't use a traditional float style level sensor due to the nature of DEF. It uses a radio frequency sensor to determine fluid level. As well if for some reason you had the situation you described, you would be getting a check engine light. The PCM knows roughly how much DEF is in the tank and roughly how much has been used. So if it was using DEF but the gauge was not moving, the PCM would be able to recognize an issue.

 

[BossHogg]

The DEF gauges in the HDs are about as un-linear as you can get.

 

[spoon059]

Not sure why this is even causing concern. Drive your truck until the 200 mile warning comes on, then add 5 gallons. The gauge is notoriously inaccurate, even in the best of conditions. It isn't actually a gauge, so much as a wild guess... just like the oil pressure gauge isn't a gauge, its a guess based upon operating conditions.

Don't worry about it, drive your truck.

 

[Road King]

I watch my DEF gauge when I fill up the tank (I use hand drum pump at work) and I swear I can squeeze in at least a gallon in that tank after it registers full.

 

[bartbill]

Thanks for all the replies.

FYI: I pull a 12K 5th-wheel 90% of the time. Average about 12mpg. So I know that about every 3rd fillup I'm due to add DEF. BUT, I'v got a gauge on the dash that does not work and I don't like that. Just one more thing to think about. And if they are notoriously bad why doesn't RAM just fit it?

 

[drittal]

They are not bad. They still work. Hell of a lot better than other that don't have a gauge at all so you don't have a clue until the DEF light comes on and you have a limited number of miles to travel or a limited number of starts before limp mode.

In your case almost a jug of DEF represents less than half the capacity of the DEF tank.

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[JRG18]

Drove from Sand Point Idaho to Brigham City, Utah and the needle on the DEF gauge never moved (2015 Ram, 6.7)



So I stopped in the Dodge dealer and talked to the service department about it. He was pretty familiar with issues about the computer throwing codes about DEF problems - 2 in the last week. Sometimes the computer threatens to shut down in 150 miles but if you keep driving it the warning just goes away.



So I bought a jug of DEF and it took about all of it - so I know it is using DEF.



Anyone hearing of this issue? Bad gauge software problem? Defective guage?



Any ideas?

Forgot where I saw it but the gauge is part of the pump housing and sits an inch or two below full so you use quite a bit before it starts to read any is gone. Perfectly normal operation....as the design goes.

Edit: Nm I found it. https://youtu.be/czJZuc8ThhI

Also, from what I've seen about the seemingly rampant codes thrown about DEF the common result is a dealer flush and fill due to contamination. Don't buy old fluid. Some say use truck stops but I don't buy unless I see the born on date. Learn how to decode it and you should be trouble free.

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