I'm guessing that there is not a traditional steering shaft connected to the steering wheel. Instead, opting for a drive by wire system. There's a sensor in the

I'm guessing that there is not a traditional steering shaft connected to the steering wheel. Instead, opting for a drive by wire system. There's a sensor in the steering wheel that detects user input and then sends a signal to another motor connected to the steering rack which actually turns the wheels. The steering wheel also has a small motor to that accepts input from the steering rack to give feedback to the driver, think "Force Feedback" systems in video game racing wheels. So, Tesla can send steering signals to the steering rack independent of what the driver is doing with the wheel. This system is becoming more common in all vehicles, not just Tesla's cars.