Code p0420
You can see if the cat is working, the exiting gases are suppose to be hotter then entering, after a fun spirited drive if you have a laser pyrometer. Has the dealership look at o2 sensor voltages? These sensors should be operating within a certain volts mV, if the secondary o2 sensor is changing rapidly something is wrong. It should be a lot steadier then your HOs2. I am not sure what type of catalyst Honda uses, if it is a 3-way or not. Using Honda's scan tools, or your own, you should be able to read what is happening.
I would first start by checking the temps at the inlet of the cat, and the outlet temps, this will give you a very good idea what is actually happening inside the cat. If you can remove the cat, sometimes a visual inspection can reveal an issue. If a rich condition or misfire ever occurred, the cat could have received to much fuel, and could have been damaged.
1.) Start with inlet/outlet temps - the outlet should be hotter than the inlet, because the catalyst is working properly, sometimes very efficient system will have lower temps at the outlet than the inlet, but this is something you can check with the manufacturer.
2.) Check for visible leaks, start the car, again look, and maybe you can hear a hear.
3.) Does your car have decreased power? You can run a test to see if your back pressure is normal, the factory will have a specification for this, and a process. This will allow you to see if the cat may have internal failed and fallen apart possibly melted.
4.) Check o2 Sensor readings the first o2 sensor should be from 98-780 mV's, and the 2nd o2 sensor should be more stable, the mV on that shouldn't be in the 800's anything below should be good, 810-830 mV is fine if it does reach that, problems are apparent when you see 870 +
I would first start by checking the temps at the inlet of the cat, and the outlet temps, this will give you a very good idea what is actually happening inside the cat. If you can remove the cat, sometimes a visual inspection can reveal an issue. If a rich condition or misfire ever occurred, the cat could have received to much fuel, and could have been damaged.
1.) Start with inlet/outlet temps - the outlet should be hotter than the inlet, because the catalyst is working properly, sometimes very efficient system will have lower temps at the outlet than the inlet, but this is something you can check with the manufacturer.
2.) Check for visible leaks, start the car, again look, and maybe you can hear a hear.
3.) Does your car have decreased power? You can run a test to see if your back pressure is normal, the factory will have a specification for this, and a process. This will allow you to see if the cat may have internal failed and fallen apart possibly melted.
4.) Check o2 Sensor readings the first o2 sensor should be from 98-780 mV's, and the 2nd o2 sensor should be more stable, the mV on that shouldn't be in the 800's anything below should be good, 810-830 mV is fine if it does reach that, problems are apparent when you see 870 +
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