THIS IS AN AWD CAR PURCHASED USED 2 WEEKS PRIOR TO THIS INCIDENT. THE CAR HAS ONLY 11, 000 MILES ON IT WHEN THIS OCCURRED. I WAS DRIVING IN BUMPER TO BUMPER TRAFFIC IN HEAVY SNOW CONDITIONS ON AN OVERPASS BRIDGE THAT MERGES ONTO A BUSY FREEWAY. THE VEHICLE'S FRONT WHEELS PULLED THE CAR TO LEFT 2-3 TIMES AT A SPEED OF LESS THAN 5MPH OUT OF MY LANE BUT I WAS ABLE TO CORRECT. WHILE STILL ON THE OVERPASS BRIDGE I TOOK MY FOOT OFF BRAKE TO INCH FORWARD (STILL IN BUMPER TO BUMPER TRAFFIC) AND STILL LESS THAN 5 MILES PER HR, HARDLY MOVING, THE CAR AGAIN PULLED HARD TO THE LEFT AND PULLED ME INTO A GUARDRAIL. IF THERE WAS NO GUARDRAIL I WOULD HAVE PLUMMETED TO THE FREEWAY BELOW. ALL THIS HAPPENED WITHOUT EVER PRESSING ON THE ACCELERATOR PEDAL AS I WAS IN VERY HEAVY TRAFFIC, SO I WAS BARELY MOVING. I HAD MY 17 YEAR OLD DAUGHTER WITH ME. WE BOTH SAID THAT THE CAR ACTED ALL ON ITS OWN AND WE BOTH NOTICED THAT NO OTHER CARS WERE SLIPPING OR SPINNING OUT AT ALL. THE SNOW HAD JUST BEGAN TO FALL SO THERE WASN'T TOO MUCH ON THE ROAD MAYBE 1-2 INCHES (ESTIMATED). THERE WAS DAMAGE TO THE DRIVERS SIDE BUMPER AND QUARTER PANEL (WHICH WE HAVE YET TO GET ESTIMATED). WE TOOK THE CAR INTO THE INFINITI DEALERSHIP, I HAD THEM RUN A DIAGNOSTICS ON THE COMPUTER. THEY SAID THERE WAS A FAULTY "CHASSIS CONTROL MODULE" THAT DETERMINES THE POWER APPLIED TO THE WHEELS AND WHICH ONES. THE SERVICE ADVISORS MECHANIC MENTIONED THAT THIS "MOST DEFINITELY COULD HAVE CAUSED THE PROBLEM WE EXPERIENCED". HE RECOMM