More than likely you'll be absolutely shocked at the code that your car depends on to function (read the Toyota unintended acceleration court documents).

Opening that interface or code turns that black box of deniability into potential evidence of shitty practices leading to failure in what should be safe, correct and easily tested modules.

Think global variables, 4k line functions, goto/jumps, completely ignoring industry standard practices like MISRA, etc.

It's horrifying.