Jessica Bombshell 89

I could use some help from anyone that knows what to do... please.... I think it was last spring break that my battery got exposed to water from the spare tire reservoir in the truck I have a multi battery system in my vehicle I'm not sure exactly how many batteries there are but I do know of three so far there is a main battery auxiliary battery and an engine fuse block battery underneath that as well so I have no dash lights on in my car right now so I plugged in a diagnostic tester and it said change battery print sensors so I did that I sound like okay maybe my dash lights will come back on it didn't do anything did I still put a diagnostic test under the car and it still said lost control lost communication with battery current sensor module so I'll go what the hell how do I fix that I just did I put a new module in it so put a new battery in the car won't start I've tried charging the main battery and it won't retain a a full charge of it will get charged but then it won't stay fully charged and the auxiliary battery I tried to connect the battery charger to that and there was no reading whatsoever that came off of the auxiliary battery so I'm assuming that it could be because of the cold weather outside or maybe the parasitic drain is the auxiliary battery I'm not too sure but also the delivery battery is half the size of my regular battery so how do I find the the part number or anything for the auxiliary battery and the wiring schematic I can't seem to find that either....any help please would be greatly appreciated...I love my car ...I usually maintain it quite well ...ever since this whole battery issue I haven't been able to keep up with the fixes...