Bad o2 sensor?

2005 4.0 200k miles. Recently threw a p0420 code. Hooked up the scanner and one of the o2 sensors voltage seems to be jumping all over while idling. Is that o2 sensor crap? Here is a link to the video I took of the scanner reading

https://youtube.com/shorts/i_X6sW6hldw?feature=share

 

If it's swinging fast and reversing at the same rate as upstream, it means the catalyst is doing nothing. Hence P0420 efficiency code.

Bank 2 looks good.

 

So it is probably a bad catalytic converter?

 

Yes, start by checking for exhaust leaks, so noise, black soot. Then prepare to replace it.

It's awful because aftermarket is trash for cats, they dont last.

If you're in a non-emission state you can look into o2 sensor spacers to trick the ecu into thinking the cat is working.

 

Thanks. bank 1 sensor 2 is driver side after the cat?

 

EDIT

Bank 1 is passenger side.



Yup, the B1 S1 and B2 S1 are Air fuel ratio sensors, so they are what monitors the engines output, they swing stupid fast and its normal.

Downstream post cat are b1s2 and b2S2 standard o2 sensor, they work opposite in voltage to the AF sensors, but their only purpose is to monitor the cats and to validate the operation of the upstream sensors.

So ideally B1 S1 is swinging fast, b1 S2 should be slowly changing and easier to read.

 

There's a few things to try before new Cats....there a whole mess of threads talking about them. I struggle with P0420 but I can manage to get the code to clear occasionally for a month. That gave me hope to try the next thing to help fix it.

Over the course of a year I did.....

-Good Name Brand Gas -
-Fuel/Cat cleaner - I did Lucas and Duralast -
-PCV Valve replaced with OEM.
-I also replaced my spark plugs and got a new gas cap early on.

My 02 sensor is pretty well seized so I couldn't do the fowler/spacer trick. PCV was the last thing I did and my engine loved it. Code cleared itself and it's still doing good. I think it was more the combination of all the things than any one of them.

Good Luck!