Between reading basic diagnostics and documenting every signal and field is routine or recurring write operations that will need to happen in the field.

Resetting the oil/maintenance light, recoding key fobs, resetting the battery stats upon replacement, etc.

I want independent mechanics to be able to do that. I also want to be able to do that myself, if I’m so inclined.

Let’s invert the car analogy: if someone writes an app with a backend service or library, should they be required to document the API for people to build their own tools on top of? Where between software and car does this requirement or regulation change and why?

I’m absolutely in favor of being able to repair my own stuff and voiding any warranty or liability in the process. I absolutely support reverse engineering and preventing companies from issuing copyright strikes on uncopyrightable facts about their products. I’m mostly OK with the idea that unqualified people can make potentially life threatening changes to their 2-ton vehicle barreling down the road at 80mph.

Would I like documentation for all these things? Absolutely! Should it be enforced by law? I don’t think so.