Oxygen sensor (O2 sensor) spacer test and results.

[@DavidStrchld]

I had good luck removing the upstream O2 sensor and spraying the catalyst with Seafoam (using a scope to see that I got it all). Resetting the codes, and doing drive cycles. The first time it will smoke a lot and normally trips a pending code (reset), the second cycle also seems to trips a pending code (if so reset). Then on the 3rd drive cycle it seems to not trip and on the 4th the monitors are set and ready for inspection. Extra: By using a meter that graphs the O2 sensor, on my car, I can see when it does it's test. Once warmed up and the gas is being held steady on flat ground the O2 sensor voltage will go from high to low to high to low many times in a recognizable cyclic pattern. This is a test time to help set the monitor. It need to complete 2 of these in 2 different drive cycles, and only has to pass once (the second time it may or may not throw a pending code - pending codes don't count in emission inspections) to set the monitors to ready. Once I see that pattern I can interrupt it by letting my foot off the gas, or depressing it more. This allows me to downshift and press the gas a bit extra to heat up the cat a little extra before returning to a steady gas pressure and have the car return to this test mode and it usually (actually always has so far) does not trip a pending code. I've used either one or both methods the last 3 inspection cycles to get though.

[@nomorelieseveragain]

I clean the upstream sensor and now the car doesn't run rich anymore...no codes.... My friend replaced both sensors and got rid of his catalytic I imagine cleaning the downstream would probably have the same effect.

[@cutearunz]

Hi I did same with my 2013 Chevy cruze, but code P0420 code came with in few miles, what to do please advise...

[@elvrolet]

If you have access to a scan tool, check your live data. That data will point you in the direction for repair without just replacing parts. If not, then check spark plugs for what type of wear they have (look up images for reference). Pull and clean the O2 sensors and try again for different result. If none of that is helpful then you will have to start spending money, replace both O2 sensors. After that it would most likely be that your catalytic converter is not functioning correctly and the code won't go away. There are a ton of variables and you won't get a solid answer until you troubleshoot further. Good luck on your repair.

[@cutearunz]

Have changed upstream and downstream O2 sensor and drove around 20 miles, doing great... Thankyou