bad cat sensor i think or whats the code mean? i think thats it, but me and red04cavy are going to do what was posted from a honda owner to make it read the right way instead of this fast way that throws a possible code. Though i did find a blown fuse and replaced it and the CEL went out but my mechanical ran a scanner to it and thats the code it gave us. So hopefully moving this o2 sensor to the right position will cure this up for good. Think that post about that rear sensor will work? ive seen couple posts on it that it will so hopefully all goes well.

P0420 is one of the most common codes you will find on a car. The code means that the pre and post o2 sensors have become within 70% of each other. Basically Check you o2 sensors, see if the post o2s has more of a straight line waveform to it or a curvy, wavy, fluctuating reading, see what you pre o2s is doing.. the most important thing to remember is not replace your cat like many people do.

i just threw the same code.. and i just replaced my stock cat with a high flow cat from magnaflow( before the code) could something be wrong with the engine or u think its just a bad o2 sensor?


here comes the boost!

from what i have learned, a lot of times it is as simple as a lazy pre o2s, could be other things, but the pre o2s would be what i check first using a lapscope, or dmm using min and max