‘21 Cascadia with DD15, not using DEF.

Yes that’s the first thing I did, but it wasn’t it. I finally fixed it. I was doing another DEF pump priming test to get rolling to the dealer to replace the pump, when I heard air hissing coming from the DEF doser. Somehow the DEF line that connects to the top part was not connected right, I simply reconnected it and voila. Doing a regen now but this is what it looks like. Hopefully this helps anyone before they spend thousands on new pump or a doser and what not.

 

So here’s the update: truck works fine for about 200 miles. That’s when I notice the pump starting to ramp up the RPM’s because the pressure isn’t at 145. It keeps doing that until the DEF requested and actual DEV doses are at about a half (requested 1,000 doses 500).

Pulled over, disconnected DEF heater hose #4 and it works again, but the cycle repeats. Could it be a weak pump, or what do I even look for at this point?