They will bill for the time lost chasing md5sums at least. You need to understand that cars are a bunch of computers now; but a laptop is not expected to kill you, and a car will. The risks associated with messing with the car are much higher.
And if you think that, lets say "BMW", will hesitate a second to block online your car heating in the middle of winter; think again. I had seen it before. Even if you could hack it, to reconfigure the system again is not always easy or obvious without some knowledge of what values you need to enter.
You're confusing how things are with how they should be, though. I'm legally liable for any modifications I made to the car, so the manufacturer or repair garage should leave my property well alone.
It's not up to the car's maker to in any way interfere with or dictate the way I use my car.
And if you think that, lets say "BMW", will hesitate a second to block online your car heating in the middle of winter; think again. I had seen it before. Even if you could hack it, to reconfigure the system again is not always easy or obvious without some knowledge of what values you need to enter.