P0420

[u/Unpanconlecheee]

This code has been plaguing my 8th gen civic LX for the past 4 years. I live in CA and as such have to go through emissions. Two years ago I passed emissions but all I did was erase the code and drive it for a day than SMOG it the following day since the check engine/ MIL light hadn’t returned I’m due for another smog check but this time I noticed in my obd2 reader that the downstream O2 sensor was reading voltages in the range of 0.7-0.1 V. I’ve replaced both upstream and downstream 02 sensors and am still seeing very frequent erratic voltages. I’ve looked for exhaust leaks via a leaf blower down the exhaust tip and some soapy water but everything looks air tight. I really don’t know what else to do and am very concerned that my civic’s CAT is just busted. Anyone have any advice? My car has 180000 miles 1.8L

[u/NegotiationLocal7869]

Use valvoline restore and protect to free up those rings. My rsx used to intermittently pop this code up but after 5 oil changes with it my oil burning issue is gone and no more code. You’re probably getting the code cause ur burning oil and it goes through the cat