I have a 2019 Ram 3500 Tradesman HO Cummins with about 25K miles and recently got the Limp Mode message. I have pulled the DEF injector and checked that there was no heavy crystallization and verified the correct ohms on the injector. While the DEF supply tube was disconnected, I set a tray underneath the supply tube and started the truck, observing that the DEF pump would pump fluid for about 20 seconds, then stop for 10 seconds. I observed this for 4-5 cycles. Does anyone know of a way to check pressure of the DEF pump or whether or not it should pump continuously, or in cycles like I observed? I'm in Alaska and the local dealer is apparently not taking new appointments, and reading other forum articles it sounds like this wouldn't be covered under warranty. When I checked codes, I had a bunch of "short to ground" or other electrical type codes. At this point, I'm wondering if something in the TIPM is causing this Limp Mode issue. I never did see a code referring to the DEF system, which I thought was interesting. I really love this truck, but all of this is giving me pause of whether I want to own a diesel in a cold climate.

EDIT: I took the it into the dealer and they found no problems with any of the systems but deleted and reinstalled the software for the truck, and it cleared everything up. I haven't had any problems going on a couple of months now. I did have a problem last winter when the truck sat for several weeks in very cold weather. It wouldn't start, it cranked for an uncomfortably long time and I couldn't get it to stop until I guess it timed out. I was worried the starter or wiring was going to burn up. After that I got a bunch of alarms that wouldn't clear so I stuck it on the charger and got it fully charged. I waited for it to warm up to something above 20 below zero and got it started. My problems with DEF started after that. These trucks, and maybe most new vehicles get goofy when the battery voltage gets too low. The software delete/install was the solution.