ANTI-LOCK BRAKES WERE ENGAGING AT LOW SPEEDS ON DRY PAVEMENT, IE: SLOWING DOWN, STOPPING. BRAKES FAILED AT A LOW SPEED WITH A HARD PEDAL. RAN INTO A BUILDING AIR CONDITIONING UNIT CAUSING MINOR DAMAGE. GMC REMOVED, CLEANED AND LUBRICATED THE FRONT SPEED SENSORS FOR THE ANTI-LOCK BRAKES.