WHILE IN REVERSE, IDLING SLOWLY TO A STOP TO PICK UP A HOT WATER HEATER, THE VEHICLE SUDDENLY ACCELERATED INDEPENDENTLY. THE VEHICLE DID NOT RESPOND WHEN THE BRAKE PEDAL WAS DEPRESSED. AS A RESULT THE VEHICLE CRASHED INTO PLUMBING SUPPLY WAREHOUSE, SENDING IT THROUGH A OVERHEAD DOOR AND THROUGH EXPENSIVE HOT WATER HEATERS AND SPAS, THE TRUCK CONTINUED INTO THE WAREHOUSE UNTIL IT HIT AN IMMOVABLE OBJECT AND STOPPED. THE THROTTLE CONTINUED TO HIGHLY REV THE ENGINE AND THE VEHICLE WAS SHIFTED INTO DRIVE TO GET OUT OF THE INTERIOR OF THE WAREHOUSE. THE VEHICLE CRASHED AT HIGH SPEED, INTO PLUMBING DEBRIS ON THE WAY OUT, THROUGH A PARKING LOT AND ONTO THE STREET. BRAKES DID NOT STOP THE VEHICLE. THE VEHICLE WAS WAS EVENTUALLY SHIFTED INTO NEUTRAL AND THE THROTTLE EVENTUALLY RESUMED NORMAL ENGINE SPEED OPERATION. NEXT DAY, TOYOTA DEALER COULD NOT THE DIAGNOSE THE PROBLEM, A FAILED THROTTLE POSITION SENSOR BECAUSE, BEING A 2004, IT DID NOT "THROW" COMPUTER FAILURE CODE. ENTIRE THROTTLE ASSEMBLY WAS REPLACED BY INDEPENDENT GARAGE. MILEAGE 62,700. MILES. EARLIER IN THE SAME WEEK, THROTTLE STUCK OPEN TEMPORARILY WHILE BACKING UP AT LOW SPEED, BUT I DIDN'T THINK ANYTHING ABOUT IT OR REALIZE THE SERIOUSNESS OF A FAILING THROTTLE POSITION SENSOR. THE TRUCK IS NOW OPERATING OK AFTER BODY REPAIRS.