neckman

My 02 CRV check engine came on with PO420 code. I replaced upstream 02 sensor with Honda OEM part about a year ago. I have noticed a decrease in mileage and sometimes engine feels as though it is holding back. If I reset light it may stay off for days or it may come back soon. Any ideas?

abusedhusband

iTrader: (1)

how many miles are on the crv. why did you change a ho2 sensor for the p0420 code? was the sensor not working? are you still getting the engine kight on for the p0420 code?

high_revs

your cat is shot. sucks, those things are expensive.

abusedhusband

iTrader: (1)

the cat could still be good. that p0420 code can be tricky. especially on a honda. i very rarely see a honda cat go bad. 90% of the time you can get away with a top engine cleaning.

high_revs

from 90% of p0420's i've seen only oem honda cat will take care of that... honda cats go bad more often then you think...we see 4-5 a week at my dealer.

someone else

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by abusedhusband &raquo;</TD></TR><TR><TD CLASS="quote">the cat could still be good. that p0420 code can be tricky. especially on a honda. i very rarely see a honda cat go bad. 90% of the time you can get away with a top engine cleaning.</TD></TR></TABLE>

I disagree. In the last 5+ years I've been at Honda I would say that the majority of P0420 codes are a failed catalytic converter. The 420 code implies that the O2 sensor is reading correctly. Otherwise you get a O2 sensor code.

high_revs

and when a o2 sensor is bad you will 95% of the times get an o2 HEATER code.

abusedhusband

iTrader: (1)

im not saying that the o2 is bad, however i have seen a lazy 02 give a false reading and set a p0420. But before i replace any converter i do a justice brothers injectoin service. For a cat to go bad something is wrong, they dont go bad unless poisoned by fuel, coolant, or oil. Some times carbon buildup causes cylinder temps to rise and throws the 02s off and the ecu knows the cat is not efficient enough for the reading its getting. The converter can be shot also. Without any diagnostic time on the vehichle all i can do is make suggestions.

phootbag

Secondary O2 sensor input monitors the performance of the catalytic converter. I have seen plastic bags land on the sensor ( located downstream of the cat under the vehicle ) and block the atmosphere vent on the sensor. I have also seen undercoating sprayed on it. I have seen asphalt coat them as well. If you can confirm the secondary O2 sensor is reacting normally then you should replace the catalytic converter. Only use a Honda part. Aftermarket is not recommended.

A primary O2 is not responsible for a p0420.

phootbag

By the way, catalytic converters go bad from normal use. No engine runs clean enough to not ruin a cat eventually.

1SloNeon

iTrader: (1)

Just an FYI....I recently got this code a couple of times in my 99 Si. I would clear the code and it would come back a couple of ignition cycles later. I had many people telling me the cat was bad which wasnt the case at all. My car does have an aftermarket cat on it (Random Technologies) which is only a year old or so. I hooked the car up to a scanner only to see the O2 sensor in the cat itself was a little sluggish when starting the car. It wouldnt read right away. I replaced the sensor with an oem one and cleared the code and no check engine light anymore. Just giving my .02 from recent personal experience with the dreaded P0420 code, lol. Good luck!!

shaggyeg6si

just put an o2 extender in on the secondary o2 sensor. Done.