Brake Abs Warning Light problems of the 2011 GMC Terrain

I was in traffic on an icy day and had to brake quickly to avoid striking the car ahead of me. Since that day, the abs light and the skidding vehicle light remains on all the time. When starting the vehicle the dashboard message shows service stabilitrak. I don't know if the abs system is working properly. I had it to the dealership in town and they told me they may need to keep it several days and that I would have to pay for them to find the problem because allegedly they had no idea what the problem was. That could run into thousands of dollars. I took it to an auto parts store and another garage and they hooked up the code reader at both places and it didn't show any code. I checked on the internet if other people were having similar issues and there are quite a few that showed up. Some stated how they had spent several thousand dollars to have it fixed and when they got it back it did the same thing. I have contacted gm and although they have "assured" me it would be taken care of, I haven't heard any further from them. Some people on the internet have said how they were charged large amounts of money to replace the module only to have the problem return. I would like the problem fixed but more importantly I would like to know that the abs is working properly if needed.