579 Main Batt State of charge sensor error

As per my picture my main battery battery percentage is greyed out.
If I engage auto start I receive the error "main batt state of charge sensor error"
This doesnt necessarily create a problem as it still keeps track of voltage and will still LVD if low enough.

The issue I'm having is that it does not engage auto start even if the truck goes down to low voltage disconnect range, since auto start goes off the percentage not volts.

My question is simple, first where is the this sensor located? I'd love to be able to at least check connections on it, but none of my online searching has netted me results.

Second, where is the auxillary battery located?
Do they use the same sensor? Ie. Could I swap them and make it so it can monitor main battery but not auxillary?

I'm a company driver 2018 peterbilt 579 with smart air and EPU. Just got the truck this way, trying to avoid a trip to dealership.
Any help is appreciated.