AFTER ENTERING THE ALLEY I PUSHED THE GARAGE DOOR BUTTON. AS I WAS TURNING ONTO THE DRIVEWAY PAVEMENT FROM THE GRAVEL ALLEY THE TRUCK SLOWED AND BECAME HARD TO STEER (LIKE WHEN THE POWER STEERING PUMP GOES OUT). ALMOST SIMULTANEOUSLY THERE WAS A LOUD POP AND THE AIRBAG DEPLOYED. WHEN I REALIZED WHAT JUST HAPPENED I PUT THE TRUCK IN PARK, TURNED THE KEY TO OFF AND GOT OUT IN A HURRY. I THOUGHT THE TRUCK WAS ON FIRE AS THERE WAS A BURNING SMELL AND SMOKE SPUTTERED FOR QUITE AWHILE. AS YET I DO NOT KNOW WHAT CAUSED THE AIRBAG TO DEPLOY. *TR