i troubleshooted my car and connected a code reader to my car and it so happened that i needed to replace both of my oxygen sensors.
i took the catalytic converter exhaust apart to see if was broken or not. the only way to make sure if its good its if you remove the exhaust system from your car and inspect it.
reasons a can go bad:
1. you car is running lean, which means your car air/gasoline mixure has more gasoline in it, so the car doesnt burn all the gasoline and all that gasoline ends up in your catalytic converter.
2. a leak in your oil. this means that oil is leaking to the exhaust system, if you don't take care of a smoking car soon, the catalytic converter will go bad because all the oil is getting acumulated on the catalytic converter and the exhause sytem.
3. vibration. mounting your exhaust system properly will decrease vibration. if there is too much vibration on your exhaust system, the honeycomb material in the catalytic converter will start to crumble.
4. time, after time, its only normal that the catalytic converter starts to deteriorate. usually they can last 15 years if you take good care of your car. they can last even more if you take extra car of your car.
this is how a good catalytic converter looks like:
as you can see from this image, the honeycomb shape material inside the catalytic converter is inttack and you can see that nothing is blocking the little thousands of holes where the exhaust passes through. if it breaks, you will not be able to see through the catalytic converter.