In year 2,000 they switched from petroleum based wire coating to soy based. Thereby creating a food source for mice etc.
After having the wiring eaten out of a vehicle twice i started using a small ozone machine under the hood. I have experience using ozone for smells and vermin control. So far so lucky.
I just put a small one under the hood and plug it in like you would an engine heater at night. Do the same with my PU out in the shed which sets for weeks or days between uses.