Did you replace the front sensor with a correct factory sensor? or did you use the cheaper universal sensor? The P0133 code is still the front sensor signal. The P0422 is the ECU's response to comparing the input 02 sensor (front one) to the output 02 sensor (rear one) and not being happy with the results. The resulting difference between the two signals tell the ECU the catalytic converter is crapped out. Do you suspect a problem with the converter? Do you have a rotten egg smell coming from the exhaust? I think I would try a factory spec 02 sensor in the frontside and see if that helps. Good luck ...... Mike