I have a problem with the def

What exactly did they fix both times? Do you have the invoice with tech stories or a itemized parts list?

 

Are u having issues with the DPF?

 

I hope it's not a DEF conversion efficiently. I had that problem in 2011 Cascada. Replaced some sensor got the same fault codes days later. It ended up being the DOC filters in the emission box was bad. Not the DPF that filter was fine. I had NOX CONV EFF 18 fault. They have a special burn the the can to to try and clean the DOC filters but they can't take them out and clean them like the DPF filter. So on mine they tried the special cleaning, that's like a 4 hours regen cycle. The DOC filters cracked and the emission box was no good. Since the DOC filters are built into the emissions box the cleaning cycle was the last hope of fixing the problem. I won't even tell you the bad news if that's the problem. They can replace the emissions box but it kinda crazy money. I'm not driving that truck anymore

 

Does the performance of the engine seem affected when the light is on? Which engine do you have? These newer emission engines do like putting on the engine light. Especially if you idle. They often will go off on their own, sometimes it takes days. If the engine runs well, and the DPF isn't clogged, I'm never too concerned over a light being on.

 

My experience with DEF systems on all trucks from freightliners to Chevy pickups is that after a few years the DEF fluid crystallizes in the lines causing them to clog and restrict flow. I've had shops clean them out and they will run great for a week or three and then they would clog up again. My theory is that the fluid crystallizes in the tank as well and that gets in the lines and the injectors clogging them up. With out proper flow the the DPF filter can't be cleaned and the excess soot will cause the sensors to malfunction.

 

That's why there is a purge cycle built in to clear all the lines of DEF so that it is less likely to freeze or crystalize. DEF has nothing to do with your DPF though.

 

I found a few similar threads, some suggest changing the def pump filter. The filter cost $100 (dd13 2014 cascadia). I'm trying to see if I can just change it, or is this a dealer only type job. Replies...?

 

I had DEF doser trouble on my Mack (MP7-405M) a while back. Mack cleaned it twice and replaced it the third time and that was that. Mind you, that was all on waranty and I have a spare roll off, so I didn't loose any time.

 

You just have to remove 4 bolts that hold the def pump cover on, it's on the back side of the def tank. And then I usually just use some larger channel locks to spin the filter off and spin a new one on.