I have only been lightly reading this thread, please excuse me if I'm repeating a previous idea.
Don't most cars use CAN bus?
Could you connect in read only mode and monitor events?
It may not be "universal", but when it works, you'd get a great deal of data from all over the car. 

I am sure there are others here with more info on this than I have.
It it feasible?

Lyle

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