I have a 2006 Trailblazer with automatic, 4WD, 325 CI, 52,xxx miles. Today I was driving on dry asphalt about 40 MPH when it started pumping the brakes and displaying "stabiltrak active". I was not touching the brake pedal anytime while this was happening. This happened multiple times before I got home and has happened several times before randomly. It is like it thinks I am driving on ice, braking and sliding. Is there an encoder on the wheel that needs adjusting or a sensor replace? I understand that my OBDII code reader will only read engine faults and will not read air bag or anti-lock brake computer codes. Any help will be appreciated.