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?
There’s always a chance of aftermarket parts being bad straight from the box, in this instance however that’s probably not the case.
The fact that the ECM set a p0420 means the O2 is functioning, in all likelihood the cat was bad already the ECM just didn’t know it due to the O2 sensor failure.