I keep getting a check engine light on my 2001 Hyundai Tiburon and I have a aftermarket header and exhaust well I keep getting a code that states catalyst operates below threshold Bank 1 and keep resetting and erasing it. I keep getting it back so what is the deal here I need some help. I also have a new o2 sensor and that didnt fix it. Any help would be cool. Thanks

 

The problem is probably the exhaust itself. You mess with the performance of the car, the sensors are bound to notice it. And since the onboard systems on cars these days determine whether you pass or fail inspection, you need to make the decision what's more important- an aftermarket exhaust or passing inspection? One option would be to run with the CEL and put the stock exhaust back on about a month prior to inspection. As long as the condition that produced the CEL is still present, the code will never clear.