Your converter might be OK, but your O2 sensor can throw a code because of contamination. This is actually the best case ...

A faulty O2 sensor can disrupt the air/fuel ratio ... as well as things like oil that smells like gas, catalytic converter damage, and the development of engine sludge. If you run your vehicle ...

Most modern vehicles have at least two O2 sensors: an upstream sensor and a downstream sensor ... as well as those leaving the catalytic converter(s). Your car's computer or powertrain control ...