Ok, here's the story. I bought a 2005 Honda Accord Hybrid with 91,500 miles used two weeks ago, and about a week ago, the check engine light went on showing code P0430. I took it to the dealer and they said the Bank 2 catalytic converter needs to be replaced. I asked if it could be an O2 sensor and the "advisor" said no. He said they cleared the code and it came right back. However, it has happened twice so far that the code went away on its own (without being cleared by me) and the MIL light came back on with the same code (third time the light came back on). I am noticing no driveability issues whatsoever. I went through the service records of the previous owner and saw that he failed an emmissions inspection and had a code P0409 (EGR Valve). The shop did a "decarbonization" service and the light apparently went off and stayed off, and he passed his emmissions inspection (about 750 miles before I bought the car). So far, I've changed the air filter (engine and cabin), changed the spark plugs, did a 3-part fuel-system cleaning service (by Sears), in addition to an oil change. The MIL light has only been back on since yesterday. So, is it possible the EGR valve issue caused the bank 2 cat to go bad? Can it be a bad O2 sensor (which the dealer said it could not be, but I'm almost certain the O2 sensors were not checked)? I just don't want to pay $1,000 to have the cat replaced, if the CAT is not a problem (CAT not under warranty). I also don't want to unnecessarily pay to have O2 sensor(s) replaced if not necessary. Does the fact that the MIL light goes on and off indicate something that I'm missing? I really appreciate any assistance anyone can offer. Thanks!!

 

You may want to remove the catalytic converter in question and take a look inside to see if the honeycomb of catalyst is ok.

I have seen a youtube video by scotty kilmer added lacquer thinner to their gas to get rid of this code. The other option I would try is removing the catalytic converter and allowing it to soak in soapy water to clear out any buildup.