The traction control in my car works by applying the brake on the individual wheel that is spinning faster than the other three. Only after the brake loses effectiveness does it reduce engine power.
Yes, but I'm not certain you can effectively steer a car this way. It would turn (I know I used to race on dirt tracks, and had the brakes set to apply more pressure to the driver's side front than passenger side), but it only helps by slowing the tire a bit more than the other, I still had to actually turn the steering wheel to get it to go. It was a gradual thing, not like making a 90-degree turn. Without a physical connection to steering, I don't think you could effectively remove pilot the car by just plugging into the computer.
I know some cars have auto-park functions, but those are still mechanical links, as you have to take your hands off the steering wheel while the car parallel parks for you, because the steering wheel turns while the car is performing the parking function. It may be possible, however, to get to that code. Does the Mercedes he was driving have auto park?