According to the manual this could indicate that the ESP module needs to be calibrated. The calibration steps are also listed in the manual. I am not at home right now but just read that chapter last night. It says to either turn the key on and not start the car, or start the car (can't remember that part). Then you turn your steering wheel all the way to the left, then all the way to the right, then center. At that point the ESP/BAS light shouldn't come back, and the system is calibrated (unless there really is a problem).