2.7 engine swap
 

Hey guy's I am new to the page. I did an engine R&R on a 2020 1500 with the 2.7. Got it all together and buttoned up and runs good.... but, I've got basically every light on the dash that could come on. Abs, traction control, engine light, engine power reduced and no electric power steering. I went over grounds and any of what I had off are hooked up, clean and tight. I changed the battery because the one in the truck was weak. So the only other thing with the truck is it sat for a few months before I got to it and drained the battery. Hoping I can find a bit of insight on this situation.

You need a proper scan tool to see what is causing the lights to come on. **Sometimes** a low battery situation will cause the ECU/PCM to 'freak out' and throw all kinds of odd codes. My suggestion is to connect a proper scan tool, write down the actual codes from all of the modules and start to research them. I believe that you will find that many are set for low voltage to different modules and loss of communication with different modules.
If nothing crazy shows up, reset the codes and take the truck for a ride, at least long enough to come up to operating temp. If it starts to run bad, over heats, etc., shut it off. Either way, connect your scan tool again and retrieve any codes that pop up. Write them down. Rinse and repeat.
There are a few decent scan tools for less than $200. Autel, Launch and Innova are normally available through your local Oreilly's, Napa or Auto Zone. Don't just pick the least expensive one available, you won't be happy with it. Once you get some experience with it, you'll want to have the advance functionality a real scan tool has over a code reader.

I have a fairly good scan tool, that's not the issue I'm having. Multiple low voltage codes, already installed a new battery and tested charging system, checked grounds and major connectors. Codes will not clear so not an option. I drove the truck a couple times, let it run but no change.