yo, got the code . & CEL came on . just dropped a new d17 in the 02 ex & ever since that, the code came up & my cat converter rattles. . . anyone know what this problem is ?


P0420 Catalyst System Efficiency Below Threshold Bank 1

 

https://honda-tech.com/forums/honda-civic-2001-2005-78/runs-well-except-when-warming-up-03-civic-2612675/
https://honda-tech.com/forums/honda-civic-2001-2005-78/another-p0420-code-2484231/
https://honda-tech.com/forums/honda-civic-2001-2005-78/eng-mngt-light-displayed-2474774/
https://honda-tech.com/forums/honda-civic-2001-2005-78/problems-new-cat-converter-2414745/
https://honda-tech.com/forums/honda-civic-2001-2005-78/cel-p1298-p0420-p0132-2483087/
https://honda-tech.com/forums/honda-civic-2001-2005-78/engine-light-off-p-0420-code-what-hell-1947047/
https://honda-tech.com/forums/honda-civic-2001-2005-78/code-p-0420-02-sensor-catalytic-converter-1940761/

There are more. You just have to Search

 

I have to say you need a new CAT.