How to Check For A Bad Catalytic Converter

In this video, I show you a way to tell if you have a bad catalytic converter in your car. While its not 100% proof, it's usually 9 time out of 10 the biggest sign. My Focus in this case, the check engine light comes on and off sporadically (with the P0420 code), so I had to check for certain.

Some bullet points...
- Go to Advance AutoParts to rent a scanner if your car has any kind of dash light warning on it. Do not go somewhere and pay to have your car scanned.

- Your downstream O2 sensor should always stay at about a half a volt, while the upstream one fluctuates

- Catalytic converters are strictly for emissions. A bad cat can cause poor fuel economy, lack of throttle response and more... but does not offer a performance gain