So I got the code P0420 back in january and had to replace the catalityc converter on my sedan 2000 lx plus a new O2 sensor, overall it came out to about $300. *****!!! (It wont let me spell the actual word) And now I got the same damn code again after I hooked up a buddie's scanner. Now what could it be?!?! The cat went out again so soon or a bad sensor, either the one I replaced or the one I didnt.

 

Did you use an OEM replacement cat or parts store aftermarket unit? Same question with O2 sensor?

When was the last full tune up?

 

Yeah I got them from autozone, Honda would charge me an arm just for the cat itself. Last tune up (plugs, wires, and dizzy rotor) were replaced not less than maybe 6 months but fuel filter has been longer though

 

What kind of warranty came with the cat? The O2 sensor you replaced was the downstream(furthest away from cat) one correct? Have you run voltage tests on both O2 sensors? Noticed the car running rich?

 

It's your cat. You can't cheap out on it but if its under warranty just return it.

 

I feel ya mine is giving me the same code but on an hx. You're just going to have to suck it up and go oem from what I've read about the quality of the platinum in the aftermarket cat's. In mine I had just replaced the primary o2 sensor too and if I knew the cat was going bad I would've just waited to replace it then and I might as well replace the secondary one too next time I get in the funds to replace the cat.

 

Buy OEM from your dealer's (or another dealer's) website. HondaPartsNow, HondaPartsCheap, HondaPartsUnlimited, etc... they're all connected to Honda dealers. The cat for my car at the parts counter is $1000, on the same dealer's website it's $700. I use my dealer's site since they are the closest, shipping is cheap, and I get the part pretty fast.

BTW, called my dealer to ask if they would honor their website's prices at the counter. Nope! And you have to have the parts shipped (still save tons), no pick up at store.

Here's a very helpful video:

 

I think its got a 3yr warranty, so they better honor it if its the cat. If not, I'll probably just sell the car I guess, cuz I'm fed up with this code and have been wanting to get a dodge dart anyways haha . Yeah it was the secondary O2, so hopefully its the primary that went bad but even though the O2 has warranty as well. Dont know how to run voltage tests on them sorry. Well idk exactly about rich, the only thing I've always noticed was a high RPM during start up, at about 2k until it warms up a bit even after I cleaned the IACV/throttle body

Thanks for the video dude, great info