What does a catalytic converter do?
Answered by Super Tire & Muffler · Updated June 19, 2026
Short answer
A catalytic converter cleans your exhaust. It uses a precious-metal catalyst to convert the harmful gases an engine produces (carbon monoxide, unburned fuel, and nitrogen oxides) into less harmful carbon dioxide, water vapor, and nitrogen before they leave the tailpipe. It is a core emissions part, which is why a failing one triggers a check engine light and can cause a rotten-egg smell.
How it can fail
Converters wear out with age, but they fail faster when an upstream problem (a misfire, a rich-running engine, or burning oil) overloads them. That is why fixing the root cause matters; bolting on a new converter without fixing what killed the old one just kills the new one too.
A rattle inside the converter, a sulfur smell, or a P0420 code are common warning signs.