I HAD BEEN RUNNING A FEW ERRANDS AND HAD JUST LEFT MY CELLULAR PHONE COMPANY WHEN I AND A PASSENGER SMELLED SOMETHING BURNING. WE PROCEEDED TO LOOK OUT THE WINDOWS FOR A BUILDING ON FIRE WHEN I NOTICED THAT MY PICKUP BEGAN TO SLOW. I TRIED SHIFTING THE AUTOMATIC TRANSMISSION DOWN TO ANOTHER GEAR BUT THERE WAS NOTHING THERE. I WENT FROM PARK TO LOW AND IT ACTED LIKE THERE WAS NOTHING CONNECTED TO THE SHIFTER. I THEN TRIED DEPRESSING THE ACCELERATOR AND GOT NO RESPONSE. I PULLED OVER TO THE SIDE OF THE ROAD AND STOPPED. I THEN TRIED OPENING MY DRIVERS DOOR WHEN FLAMES SHOT UP BETWEEN THE DRIVERS DOOR AND THE CAB. I TURNED OFF THE TRUCK AS SMOKE STARTED TO FILL THE CAB AND I BAILED OUT THE PASSENGER SIDE DOOR. MY PASSENGER AND I MOVED WELL BEHIND THE PICKUP AND WATCHED AS FLAMES SHOT OUT FROM UNDER THE PICKUP AND SMOKE BILLOWED OUT OF THE ENGINE COMPARTMENT. I CALLED 911 ON MY CELL PHONE. IN THE MEAN TIME A WITNESS HAD PULLED UP BEHIND US AND INFORMED ME THAT HE WAS TRYING TO FLAG US DOWN BECAUSE HE HAD SEEN FIRE UNDER THE TRUCK FOR AT LEAST 3 CITY BLOCKS. I DON'T KNOW WHAT WOULD HAVE CAUSED THIS TO HAPPEN. I HAVE OWNED THE VEHICLE SINCE IT WAS NEW. IT HAS BEEN WELL MAINTAINED AT THE DEALERSHIP WHERE I BOUGHT IT. IT IN FOR SERVICE IN DEC. OF 2000 FOR AN OIL CHANGE AND INSPECTION, NO PROBLEMS WERE NOTED. THE VEHICLE HAS NEVER BEEN OFF ROAD, FOR IT IS A TWO WHEEL DRIVE. THERE HAS BEEN NO MAJOR MECHANICAL WORK DONE, JUST SOME MINOR ITEMS SUCH AS A WATER PUMP F