since you're kinda stuck with it and this deep. I feel like it might be time to get a cheap clone tech 2 and access to a full shop manual. something like alldata will have all the trouble shooting trees for every fault code. all the wiring diagrama and an explanation of how each system works and is trouble shoot.
it's like 19$ a month for access for one personal vehicle. kinda stuff shops use, but pay $1000s for unlimited access. it's really worth having for things like this.
Single-vehicle access to OEM diagnostic and repair information for the student and the do-it-yourself mechanic. Includes wiring diagrams, TSBs, DTCs. Powered by ALLDATA.
www.alldata.com