P0420 code after replacing downstream O2 sensor.

Some0neAwesomeB to Mechanic Advice@gearhead.townEnglish · 1 year ago

2003 Honda Accord LX 2.4 liter. I had an O2 sensor heater circuit engine ligjt for quite some time. I finally replaced the O2 sensor, and now I’m getting a P0420 engine light code (low catalytic efficiency) after a drive cycle. Is there a chance that my new Walker brand, O’Reilly auto parts O2 sensor is bad, or is it more likely my catalytic converter has failed?

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