I would go even further, if car model is sold more than 100k times and more than 5 years (a.k.a reaches "significant" portion of population) car manufacturer (or any other equipment manufacturer) must do following:

1. Wiring diagrams, service documentation, working diagnostic software, firmware blobs must be provided to national archive institution (think archive.org) - and how information is shared is in discretion of this institution

2. In case there are theft prevention or "genuine check" systems (requires keys, codes or whatever) - keys and procedures are given to police (it they job anyway to prevent stealing)

3 Car road worthiness is tested using open (or opened) hardware/computer blocks - car must pass all safety rules and excepted functionality cannot deviate more than 20%. The manufacturer must provide documentation, SDK and calibration procedures, safety tests, but it is illegal to lock functionality by requiring special hardware (if it is secret sauce - provide schematic for alternative hardware which good at least 80% as special). Obvious, it can have proprietary software - it need provide open source alternative implementation.

4. if car is sold, user need to be informed about open hardware and software.