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

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 ...

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 ...