Got a P0420 thinking about replacing the O2 Sensor before the Catalytic Converter?

Autozone and Honda charging ~100+ for the piece but Denso brand is only 50 dollars with the same fit.

2010 Honda Accord V6 EX-L

Should I buy the Denso or a OEM brand through Honda Stealership?

I just changed my upstream o2 sensor off my 2004 honda civic ex. The brand I pulled off was Denso. I'm not sure what brand I have on there now, but it was hard to find a correct match. I got it from AutoPartPro via Amazon. Was 100 dollars cheaper than the Bosch o2 sensor at Autozone. It cost 120 with shipping. Anyway, just make sure the part is compatible with your vehicle.

There are 2 sensors, one up top, the other down near the pipe. Oh and if you want Honda parts at a killer discount, check out a site called BK Honda. Just put a brand new Cat in the wife's car for $250.

Oh, as a test, switch the O2 sensors from the rear cat to the front. If your code remains the same, then it's the cat.
If the code changes to 430 then is a sensor

Edit: I have also heard that some law was recently passed that requires Mfgs to warranty cats for 5 years, might want to check with your dealer on that.

Has anybody diagnose and come to the conclusion that the O2 need to be replaced? Remember your car is a V6, that's mean you have 2 upstream O2 sensors and 2 downstream O2 sensor. How did they diagnose for code P0420? A failed CAT or an exhaust leak will also trigger code P0420.

I do not know where you're at but do not forget the factory Emission warranty and exhaust warranty. Depends on the failed parts. Emission is 8/80K miles and related exhaust parts that may have a life time warranty. READ your warranty booklet.

It could be a failed CAT (Emission warranty)
It could be an exhaust leak (Exhaust warranty)

Check with your local Honda dealer about the warranty or if you can't find the warranty booklet. Go to this site and download one from Honda for free:
http://owners.honda.com/...cord-Sedan

Look at two of several TSBs (Technical Service Bulletin) issued by Honda for code P0420

2010 Honda Accord Engine And Engine Cooling Service Bulletin 370868
NHTSA: Action Number: 10055916 Service Bulletin Number: 370868
Report Date: Jun 05, 2014 Component: Engine And Engine Cooling
Summary: Honda: information provided concerning an investigation, on certain vehicles, of the catalyst system efficiency below threshold (dtc p0420) with malfunction indicator lamp (mil) on and either collect specific parts or inspect parts, prior

2010 Honda Accord Engine And Engine Cooling Service Bulletin 374363
NHTSA: Action Number: 10055846 Service Bulletin Number: 374363
Report Date: Apr 18, 2014 Component: Engine And Engine Cooling
Summary: Honda: some vehicles may experience a malfunction with the catalyst system. Malfunction
indicator lamp dtc p0420 may be stored. American honda is attempting to inspect the vehicle before any repairs have made. *js

This link contain all TSBs on your 2010 Accord:
http://www.automd.com/tsb/honda_m/accord_mm/2010_y/

I would suggest you to contact with your local dealer before hand. The problem could be cover under the factory warranty. HTH