Pontiac Repair: P0135 (Bank 1) (Sensor 1), catalytic convertor, oxygen sensor

Question
I just had my catalytic convertor replaced.  My car is running like crap and when I had the codes checked I got P0135 (Bank 1) (Senor 1) I had a mechanic tell me he thought something might of gone wrong with the installation or my oxygen sensor was wrong and to take it back where I had the convertor installed.  The person who installed my convertor swears that he welded the convertor in place and did not have anything to do with the oxygen sensor.  From what I read it sounds like when the convertor is installed in does come in contact with the sensor at the engine part of the convertor.  Please advise.

Answer
Hi Karen:

what model and year is this. it's a he said she said as to what happened to the sensor. it may have been related to the convert or it may not have. reguardless the sensor is more then likley bad wether it's cauing it to run bad or not you will not know untill you replace it and see what happens after that. if any more codes come back. depending on how it went bad can effect how the fuel delivery is in the car. good luck :0