How will I know if the catalytic converters are bad? I went to a muffler place and they told me everything good but the manifold. But, previous owner said they are bad.

 

Do they rattle?

Are you throwing catalytic converter codes?

Do they glow orange when they get heated up?

If the answer to all of these questions is no, then you're good to go.

 

Good question. On my OBDII scanner, I get no codes, a green light on past codes and all looks good. Only thing is when I do I/M ready, it green lights all systems except a red X next to "Cat". For now not worried because it always passed inspection - but I was curious why it flagged the Cat.