What you are trying to do is difficult and will require some microelectronics hacking. might also need to read some of the chips to pull proprietary flash memory off.
You probably will have the most luck using a drive by wire car where the steering wheel does not have a mechanical connection to the wheels. Instead it will just have a position sensor. You will need an oscilloscope to see what kind of signal this sensor passes to the computer to determine wheel position. Once you get the proper wave with the proper voltage and amperage then you can start programming a program to simulate this. You will probably be using a raspberry pi for the signal control but you potentially could use a serial port or even a usb port but you might need to make a custom board to get the voltage and amperage to match up.
you will need the circuit to cut signal from the actual steering wheel when it is being used and restore signal to the steering wheel when it is not used. You will also need a circuit to control the steering wheel position with the built in force feedback motors they have. this will also keep the steering wheel lined up.
One more thing to take into consideration is if the steering wheel is in the wrong position when going back to normal driving then it may not steer correctly so this might need to be rectified by saving the position the steering wheel ends up in and restoring that to the computer using something to "ramp up" the position as if steering to the current steering wheels position.
It would be way easier to simply add a pulley or chain system to the steering wheel column of any car and control it that way using a servo motor.
With the chain solution you could retrofit anything even model t fords. All you would need is the servo motor a motor control board and a couple switches to signal maximum turning angle. the computer would run the wheel back and forth to determine where center is and where both stops are. you would need a trim setting due to alignment not being perfect and your off using a ps3 controller to drive your car.
The only way to do this using the obd2 is if the company that built the car added in special code for testing that model using some of the reserved inputs. To me this sounds exceedingly unlikely but as more cars become automated there is a chance some new models may have this. You will need to hack into whatever code they have and try to figure out what signals are used to get the car to do what you want. At that point you should get their proprietary service obd2 scanner and decompile it to get the code you need to send their obd2 computer.
stick with the chain drive on a model t it will be way easier.