Your catalytic convertor is a very sophisticated part of the exhaust system. is an emissions control device that converts toxic pollutants in exhaust gas to less toxic pollutants by catalyzing a redox reaction (oxidation or reduction). Although it appears to be similar to the muffler, its function is very different. There are sensors that if working properly will monitor the catalytic convertor, but if the sensors are contaminated, or defective, they will produce a false code. You should have your exhaust system diagnosed to ensure you are replacing a part that is indeed defective. There are a lot of times when a sensor and even vacuum leaks are the actual cause of these catalytic convertor failure codes.