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?
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.
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.
Scars are a reminder of how not to do it next time.
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.
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.
Originally Posted by phootbag
A "dizzy" is that magical thing you replace when your car wont start.
Originally Posted by chrisff521
Ok so youre saying I should replace the whole "dizzy" ?
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!!
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