My father inlaw had a 1980 Mercedes and a 1995 Bronco in his barn. Both were infested with Mice.
I pulled the interior of both and dropped the headliners.
I tossed a lot of baby mice and many nests.
The critters had ate the wire harness so the Bronco wouldn't run right.
They had gotten into the heater and A/C.
Bottom line it was a mess.
Took a garden sprayer mixed with 50/50 water and bleach. Sprayed the gutted interiors for 2 weeks and let dry.
New carpet, and problem was solved.
Had a upholstery place call me and ask what to do about Mice turds an pee.
I told them about the bleach. They tried it and gave me a Thank you check. They had tried everything to no avail.