P0420 code after fuel inj cleaning

I have an '02 4 cylinder Solara. I took the car to an independent for a fuel injection cleaning & now have a check engine light on which they say is a P0420 code for the catalytic converter performing below threshhold. I had the catalytic converter replaced at 50,000 miles while still under warranty. The car is now at 105,000. I was just wondering if faulty fuel injection servicing can cause these issues. The check engine light appeared about 3 days or so after cleaning. Any input appreciated!