DD15 EPA 10 DEF Quality Issue

Matthew Mobile Technician Bartlett, Illinois Posted   Latest  
Unsolved
Heavy Duty
2012 Freightliner Cascadia 125 14.8L (DD15)
Def Quality Warning

Hey everyone,

I have this truck here that has a DEF quality code and will flag SCR efficiency during regen. The DEF doser block and nozzle were replaced, when I did a quantity test it would just dribble out DEF and spray mostly air. The DEF pump pressure never drops. 

I went to try and clear the code today by running a stationary regen. The data has actually gotten worse, I think the doser block is bad but need a second opinion. The shop said the part looked like it had been installed and had DEF crust on it and a terminal bent... so more evidence, but here is what I am finding. 

During regen the SCR efficiency will be around 90% or more, until the DPF outlet temps hit around 600 degrees. Then the outlet NOx sensor will rise until it is actually higher than the input. When I disconnect the DEF doser the NOx sensors are dead on, so it does not seem like a rationality issue or exhaust leak. My theory is that the doser is delivering too much air or stops delivering DEF. Any ideas? It is just weird to me that it only happens after the exhaust gets hot. 

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Rex Technical Support Specialist
Alliance, Ohio
Rex Default
 

Don't know the DD system at all but in most the DEF dosing system only pushes fluid. May be some air at end of cycle to purge. Sounds like the DEF is not getting into the system. On Cummins residue can build up in the pipe beyond the doser to the point exhaust flow is restricted. If soot is getting past the DPF (it shouldn't) it can get into the catalyst coating the tubes. This can drastically…

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Matthew Mobile Technician
Bartlett, Illinois
Matthew Default
 

This system has an air line going to it. It mixes the air and DEF together at the dosing unit. The part going into the aftertreatment assembly is just a nozzle and it is brand new. Unfortunately unlike a Cummins, the decomp tube cannot be easily accessed for cleaning, it is a Detroit one box unit, it has to be cut apart and welded back together. NOx pre DOC is around 250 PPM during regen…

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Michael Educator
Chillicothe, Ohio
Michael Default
 

Did the truck have codes for low def pressure by chance?

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Matthew Mobile Technician
Bartlett, Illinois
Matthew Default
 

No, and I took the tube off to the doser assembly during a volume test and it had plenty of flow. Actual pressure was confirmed with a pressure transducer in place of the sensor, it is always around 70 PSI. I scoped pump current too, nothing out of the ordinary. The amperage matches scan tool data and the commutators on the motor seem good.

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Matt: See if this helps. youtube​.​com/watch?v=rCFfmw… Guido

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Matthew Mobile Technician
Bartlett, Illinois
Matthew Default
 

Thanks, I am guessing this thing got installed and put back in the box... maybe the part sitting on the shelf made it crust up...

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
   

Hi Matt: I'll give you something to think about. I got called out for an Onsite Service a year ago. It was an F450 which was having a problem with the DEF pump. They had put 4 pumps in it. (This vehicle never got out the door!) I verified the pump worked and then it didn't. Long story short, it was contaminated DEF, which was purchased from the dealer when he bought the reservoir. It was…

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Chris Diagnostician
Lansdale, Pennsylvania
Chris Default
 

First question is what is the actual concentration of the DEF being dosed? Were the lines flushed with warm water to remove any crystallization that may have occurred? Another question would be whether there are signs of coolant contamination in the decomposition tube or SCR (assuming coolant cooled DEF injector). Or heavy build up of burnt urea in the decomposition tube (often seen this with…

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Mike Technician
Salina, Kansas
Mike Default
 

Rember something read on a Web site , about a person going on a long trip they had been getting the lower price def. Then on this trip they went and gotten the higher price def and then started having problems. Like some else posted bad def , did someone put a filter on def system and now it's plugged? Something else are you sure it's def in system did the driver pour water into tank because…

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Matthew Mobile Technician
Bartlett, Illinois
Matthew Default
 

The DEF was tested with a refractometer and 1/2 of the tank is fresh DEF... but that doesn't always mean much lol

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Matt: When we pulled the DEF from the reservoir, you could feel it was gritty. Needless to say, the pumps weren't enamored with it for long. Guido

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Caleb Diagnostician
Mishawaka, Indiana
Caleb Default
 

I'm more familiar with pickups than heavy trucks. However reading your post I get an idea. My question is this. Are you saying the doser nozzle still only dribbles out? If so I am assuming you obviously cannot complete a quantity test correct? If yes too both of these questions then I I would say for sure you have a problem between the pump and the nozzle. I know I have definitely had on pickups…

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Matthew Mobile Technician
Bartlett, Illinois
Matthew Default
 

I didn't get a chance to re-check the quantity test yet, the exhaust was hot from two hours of regen lol. The shop put a new dosing unit on it today, I am going to re-check tomorrow.

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Caleb Diagnostician
Mishawaka, Indiana
Caleb Default
 

No problem I understand haha.

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Nicholes Technician
Reading, Pennsylvania
Nicholes Default
 

Well I happen to have a lot of experience working on these systems . I would make sure the def tests good first. second if it tests good then I would run a def quantity test with the def doser injector removes out of the one box and verify you have the correct amount. you already said the nox sensors were reading with in range of each other with the doser unplugged so they would check out…

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Nicholes Technician
Reading, Pennsylvania
Nicholes Default
 

So did you ever find a fix?

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