> Like I think some modern cars are fly-by-wire, so you could stick the accelerator open and disable the breaks and steering.

Essentially all passenger cars use physical/hydraulic connections for the steering and brakes. The computer can activate the brakes, not disable the pedal from working.

But also, this argument is absurd. What if someone could reprogram your computer to make the brakes not work? They could also cut the brake lines or run you off the road. Which is why attempted murder is illegal and you don't need "programming a computer" to be illegal.

> It would be difficult to catch in an inspection if you could reprogram the OEM parts.

People already do this. There are also schmucks who make things like straight-through "catalytic converters" that internally bypass the catalyst for the main exhaust flow to improve performance while putting a mini-catalyst right in front of the oxygen sensor to fool the computer. You'd basically have to remove the catalytic converter and inspect the inside of it to catch them, or test the car on a dyno using an external exhaust probe, which are the same things that would catch someone reprogramming the computer.

In practice those people often don't get caught and the better solution is to go after the people selling those things rather than the people buying them anyway.