[claykin]

Wow, unfortunate. It's a semi-common issue not just limited to bmw. Partly has to do with environmental requirement changes to the way wiring harnesses are made.

Search Google for rodent tape. Several companies make it and you re-wrap the harnesses being attacked by rodents with this tape. The rodents don't like the scent or taste so (hopefully) they won't chew.

Honda has an oem version. Google it. Many others have it too. Unfortunately, the oems aren't using it on production harnesses.

I've heard of people buying wire loom and wrapping the loom in this tape. Then they cut as needed and place over the car harnesses and tie wrapping to the harness.