How to determine if P0430 is O2 or catalytic converter

This is by far the best video I've seen which gives two ways to tell if your catalytic converter is bad. In a nutshell, Eric the Car Guy uses two methods to diagnose a bad converter:

• He uses a scan tool which uses live data to do just what you are looking at. He is checking to see how the downstream O2 sensor is behaving. Basically it should be fairly steady, while the upstream one is wildly all over the map.

• Secondly, he uses an infrared no-touch thermometer to read how hot the exhaust where it goes into the cat and where it comes out. If the cat is good, your readings coming out of the cat should be much hotter exiting than going into it. If the catalyst is doing it's job, it's going to be burning the excess hydrocarbons, which will cause heat.

If you do either of these test, ensure the vehicle is completely up to temperature. If you don't, you won't get accurate readings.

I do disagree with Eric on one point of the video, that being "the catalytic converter is there to clean up NOx emissions" ... while a cat does do this, it is there also to clean up Carbon Monoxide (CO) and Hydrocarbons (HC). For this reason catalytic converters are called three way converters.