Peterbilt 2015 cm2350 list of issues

[JimT]

I'm late to the party here and just read through the entire thread, so pardon me if I missed something. But one thing that jumped out at me was the 2 different sensors throwing codes for erratic data as well as multiple sensors reporting wildly inaccurate data in insite. At that point I would have stopped everything else and focused solely on the electrical system and wiring. Pull up wiring diagrams from quickserv and a multimeter. 1 bad sensor, sure, but multiple bad or erroneous sensor readings at the same time, that can't be a coincidence. It also lends itself to the ongoing and sometimes intermittent nature of your core power loss issue. ECM could just be adjusting operation due to erroneous, but still in-spec, data. This seems especially common for aftertreatment related derates, though I'm not saying that's where your problem lies.

As for the fan, first and foremost data monitor with insite to find out what the ECM thinks is commanding the fan on. Also, if that's a Pete it probably has that air solenoid up near the firewall that controls the air supply to the fan clutch. I've seen many people have issues with them going bad and simply replacing that switch fixes their fan issues. Might be worth checking. Eventually they do go bad causing engine fan to stay on, so even if it isn't the cause it might not hurt to at least have a spare.