This may be way to simple but have you considered just Changing the engine wiring harness for now?
under $100 on eBay

it’s plug and play. If something was under the hood chewing away, that something may have chewed on wires easily accessible

just a thought. It would be easier than looking for chewed wires. I understand that it could be concealed somewhere else but for $100 it could be a cheap fix. Cheap part cheap repair, no hunting



https://www.ebay.com/itm/Engine-Wiri...kAAOSw3d9d6fbI