I had a Honda crv 2010 with mileage just above 100,000. Few days ago engine light was on and autozone told me it is p0420. I did not feel any problem while driving, no low gas usage, no not able to accelerate, etc for typical dead Catalytic converter. I went to Madis and the person told me the catalytic converter was bad. They showed me the the AF sensor signal M is 1.8-1.8 and Af sensor signal P is 2.20-2.20. Basically two flat lines. Is this the indicator of bad CC? Thanks for your help!
Is this the indicator of bad CC
Not really!
The UPSTREAM cat O2 sensor should bounce around.
While the DOWNSTREAM O2 sensor should be a flat line.
IF both the upstream and downstream are bouncing then that would be an indicator.
Otherwise, it requires further investigation, connect an OBD2 scanner with graphing and inspect the lines about 15 minutes after starting the engine and when the fuel system goes into "CL"/"CLOSED".
Well, that code shows an inefficient catalytic converter and I've seen people drive them years and years that way with no problems at all. But if you live in an area where you do emissions testing, you'd have to fix it to get your car registered each year. I love you! Could try some catalytic converter cleaner and see if that helps along with the tank of shell v power gas that burns cleaner. Just realized catalytic converters are very complex interrelated system in your car that many things can cause them to go in efficient and often just replacing. The cat does not fix the problem and it comes back the next year because something caused it to go bad
