Most OBDII scanners can't read the code because it is not emissions-related. Many scanners that can read ABS codes can also read stability control and traction control codes. I have a $100 scanner that can read OBDII, ABS, Stabiltrak and SRS codes.
If you take it to a local garage, check to see if they can read ABS codes first; if so, they can probably read the stability control code.
IF the code turns out to be steering wheel position sensor, IF it goes out when you drive for a bit and then restart and IF it only comes on occasionally (less than once a month or so) then I would not bother doing anything.
Understand the steering wheel position sensor is a combination of computerized technology and good old electro-mechanical sensor technology. This simply means that it is a very sophisticated example of what is basically like a variable resistor. Because most of us tend to drive a good portion of the time with the wheel relatively straight ahead, the outer edges of the electro-mechanical sensor don't get used as much. Like many other variable resistor-type sensors, very little use can lessen the contact.
This means that you come home one day and park with the steering wheel at a slightly greater angle than normal, and then leave it for a day or two. In the morning, your warning light goes on. If you drive for a few seconds and then restart, the light will go out.
This is why I recommend not doing anything if it meets the above three criteria. A new sensor will obviously cure the problem, but in a few years, it may come back again. It is just the nature of the sensor, and it not confined only to GM vehicles.
If the light come on more than once every month or so or if it does not go out after driving a bit and then restarting, then I would look at changing the sensor. But all this hinges on first getting the code read. If it is a steering wheel position sensor, don't panic quite yet and change it out (unless you are still under factory warranty of course. If you are under a third-party warranty - good luck getting them to pay for this!)