Catalytic converters fail for many reasons. In a lot of cases, the failure has little to do with the cat itself, but instead is the result of another fault within the vehicle. It’s important to rectify any problems before a new cat is fitted. Overheating is just one problem that’s related to a vehicle fault, and therefore not covered under a manufacturer’s warranty. Overheating is caused mostly by unburned fuel entering the cat due to an engine misfire. Below is a checklist to help identify and eliminate possible vehicle faults that may be causing your catalytic converter to overheat.