[way2old]

You actually need a scan tool that will allow reading of the PIDs on the vehicle. Usually an O2 sensor will not cause a P0420 or a P0430. If a scan tool shows both front and rer sensors changing at the same rate, the converter is usually at fault. Try erasing the codes and see how long it takes to come back. I don't think it will cause any problems unless the converters are plugged. If they are plugged, you are likely to have problems.