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P0430 code Accord

2012 Honda Accord coupe V6, 110k miles.

CEL came on today. Code P0430 (catalytic system efficiency bellow threshold Bank 2).

I understand this is the O2 sensor downstream detecting that the cat converter isn’t working properly.

Any suggestions?

Replace O2 sensor(s). Exhaust leak?

Use cat converter cleaner?

I guess if those don’t work replace cat converter.

Otherwise no problems with the car.

I had the car in the dealership for an airbag inflator replacement recall yesterday, but I don’t see that that is related.

Luckily it passed the emissions inspection (NJ) a couple of weeks ago.

“Cat cleaner” is unlikely to help.

Exhaust leak? Unlikely, but if you have one it would be a good idea to address that issue.

Replace downstream sensor[s] for starters, clean the code, keep driving.

If code returns, the next likely thing will be to replace the converter.

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The down-stream O2 sensor is just the messenger reporting what it’s detecting. And when this code usually shows up, people want to kill the messenger.

Unless there’s a code that also indicates that there’s a problem with the down-stream O2 sensor, P0430 has to be the code to believe.


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Ask a shop to monitor the pre cat vs post cat o2 sensor signals. That’s how the computer figures out to throw a 430 code. If those show the cat is worn out, replace the cat. Sometimes this is caused by o2 sensor problems, but usually it is just that the cat needs replacement. The problem with replacing the o2 sensors on a flier is that the replacements may be faulty and you have now introduced a problem that didn’t exist before.

On a 6 year old vehicle probably a good idea to have some testing done to determine why the cat failed. Are you using an usual amount of oil , like more than a quart in 1000 miles? Any weird looking smoke out the tailpipe? Any other codes, like for misfiring been going on? If nothing, then at least get a fuel trim measurement, which is a way the shop checks for deviations from the proper air/fuel mixture.