A catalytic converter is an exhaust emission control device that reduces toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction (an oxidation and a reduction reaction). 
Signs that your catalytic converter needs to be changed.
- The smell of sulfur or rotten eggs from the exhaust.
- Sluggish engine performance.
- Excessive heat under the vehicle.
- Reduced acceleration.
- Dark exhaust smoke.
