‘21 Cascadia with DD15, not using DEF.

Hi all, I have an issue that started about a week ago where my truck isn’t using any DEF. Initially I thought it’s a bad DEF pump or a clogged def injector, but when I took apart the pigtail that connects onto the injection nozzle part a lot of water came out. I cleaned it, let it dry, and voila, my DEF pressure was 142 with RPM’s around 1200 on the pump.
I figured that was causing my issues, but now truck still isn't using any DEF. Every 200-300 miles or so it’ll throw the codes for under pressurized def pump and a derate. It’s a DD15 engine, using newest version of DDDL. Any ideas on what could be causing this?
Every time it throws codes I just unplug the pigtail and plug it back in, run the ADS check and it clears the codes but still no DEF usage. Thanks for any input!

 

I tried that once, doesn’t show like it’s using DEF at all on both requested and actual usage.

 

Just read through this, i was not aware that there’s a filter in the actual dozer. Will take it off and inspect, the way I found out about the water in the connection to the doser itself is because I was going to do the quantity test. Will take it all apart and re-test, might be the cause because I ruled out almost everything else I can think of. Thank you!

 

Funny thing. I have a Detroit software, every time that happens I unplug the doser unit, plug it back in and it usually clears the code on self check. But lately I had to prime the DEF pump once or twice and that seems to get it done. So I figured it might be the pigtail, and just replaced the wiring, but still having the same issue. Thinking about replacing the doser unit at this point unless y’all got better advice? I’m lost on this one.

 

Oh yeah that was replaced about 100k miles ago or so. So I’m at a loss here and really don’t want to start throwing parts at it for the issue to just continue. Any other ideas?