my car never throws codes... ever. I honestly dont think it has ever thrown a code since I got it 6+ years ago. Someone told me that is not unusual though. I didnt think to look underneath at the cat. That could be possibility. I have noticed a slight decrease in power but have attributed that so far to the 160,000+ miles on it. What else would signal a bad cat besides low power (as I have had in the past with bad cats)? Fuel mileage seems consistent and I would crap a brick if my car spit a code. This hasnt occurred again( knock on wood) but I have not been on the highway or any other sustained high rpm conditions to spur it.