2020 Ram 5500 Diesel - SERVICE DEF SYSTEM: SEE DEALER

[2019 Ram and Newer]

I’m working on a 2020 ram 5500 diesel truck. I’ve worked on several of them for a magnitude of reasons. But this is my first go around with the SERVICE DEF message. This is what I’ve done and checked so far. Checked the def injector. Wasn’t really crystallized. Cleaned anyways. Put the scanner on it. Def line pressure is around 86psi. Nox readings upstream are around 120-140ppm. When Downstream starts reading, it’s around 800ppm. Then it works down to around 80ppm. Neither of these readings activate until the dew point for that nox sensor is reached. The upstream sensor reaches dew point and stays there. Down stream does not. It will drop out of dew point and stop reading. I physically removed def injector and checked to make sure it was spraying. It is but it is just a very very light mist. I’m not sure how strong the spray should be. There were 3 codes. They are: p1c54, p24b1, and p2bac. The owner said they just recently had some AC work done. I’m almost curious if they left the batteries undone for too long and the ecm needs flashed again. I could use some help on this. I’ve dealt with a few of the DPF issues on these diesels. And had to figure it out on my own. Just recently found this forum so hopefully don’t have to do that again.