P0137 3 years after cat was stollen and o2 replaced

Look at the freeze frame data from something like an AP200 scan tool so you can see the numbers that the sensor is producing when it's working.

 

If the app and the thing you're using plugged into your OBD2 port is called bidirectional it has the capability whether the software you're using on your phone has the capability to interpret freeze frame data I have no idea like if you're using the carista app I believe you are good to go but if you are your payong a subscription fee.

 

How much oil is the car burning between oil changes and at what intervals.

 

That's around a quart of oil every 5K or 10K oil change interval?

The reason I'm asking is that you can oil foul the CAT if your oil burn is excessive. That would lead to a down-stream sensor issue.

 

You need to first determine if it's a sensor issue or a CAT issue. There are chemical treatments to try to fix an oil fouled CAT, because the replacement alternative is very expensive here in Ca.

If you try any of those Youtube tricks to fool your sensor, that's an automatic FAIL at the smog station. Just saying....

Hope this helps....