Diagnostic code P0420

What ended up being the problem? I got a fullrace catted dp and im getting the same code.
 
I thought some people with the high flow cat said they had no codes show?
 
Yeah, I think you are right. So, the consensus is may or may not trigger the code.

No one should be running a downpipe without FlashPro and a tune anyway.
 
I have flashpro and did the reflash and its still one. Gunna flash the new calibration and see if it works.
 
WOW, I saw that code and instantly knew what it was. My 1999 Accord check engine light came on and the computer threw that code while on a car trip in 2004. I had an auto store read the code in Gallup NM and then called a dealer in San Diego because that is where I was headed. They said I'd be fine but bring it in when I get to San Diego. Ended up having the catalytic converter replaced under a Honda warranty.
 
I've had my skunk2 header and exhaust on for about two months plus. Got a CEL in stop n go traffic for 20-30 min. Why would it start now? I'm using the reflash map because I'm early into calibrations wit Vit. Any help appreciated.
 
Tom's Si said:
I've had my skunk2 header and exhaust on for about two months plus. Got a CEL in stop n go traffic for 20-30 min. Why would it start now? I'm using the reflash map because I'm early into calibrations wit Vit. Any help appreciated.
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Pretty sure flash pro has an option to disable the secondary o2 sensor. Am aftermarket cat or a no cat situation will measure a bit differently on the 2nd o2 sensor and cause a check engine light.
 
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