Diagnostic code P0420

[John_chafin]

Thanks guys for the help!

 

[Pat Mills]

What ended up being the problem? I got a fullrace catted dp and im getting the same code.

 

[webby]

What ended up being the problem? I got a fullrace catted dp and im getting the same code.

catless downpipes give this code. You have to remove the code with flashpro

 

[squiggy]

catless downpipes give this code. You have to remove the code with flashpro

Catted Full-race will trigger code as well.

 

[webby]

I thought some people with the high flow cat said they had no codes show?

 

[squiggy]

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.

 

[Pat Mills]

I have flashpro and did the reflash and its still one. Gunna flash the new calibration and see if it works.

 

[squiggy]

I have flashpro and did the reflash and its still one. Gunna flash the new calibration and see if it works.

You need to turn off the O2 sensor in FlashPro.

 

[razingkane]

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.

 

[Tom's Si]

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]

^^^

 

[323]

^^^

If you're tuning with Vit, you should ask him

 

[Bulkybear]

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.

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.