Confirm the converter is not physically damaged or melted
Check for engine codes and fix the underlying cause first
Use a catalytic converter cleaner additive in the fuel tank
Drive the vehicle at sustained highway speed to help burn off deposits
Remove the converter only if it is accessible and legally permitted
Soak the converter in a catalytic converter cleaning solution
Rinse thoroughly with water after soaking
Let the converter dry completely before reinstalling
Clean the oxygen sensors if they are contaminated
Replace the converter if it is clogged, broken, or failed
Use only methods approved for your vehicle and local regulations