i want to know if the o2 sensor would have anything to do with problems in my ATX... i.e. gear hunting between 35-45 mph and no overdrive gear. Also many times times hold flashes on the dash so naturally there would be no OD. i'm not a tranny expert at all but the mazda dealer said that the o2 sensor is the problem. if so could i replace it myself? or should i go to the dealer and give them alot of money?