p0420 code
 

I am trying to determine whether it is my converter or my rear o2 sensor throwing this code. I replaced the converter on my car roughly a year ago. I don't see any vacuum leaks and my coolant temp sensor appears to be working correctly. Sometimes my idle is a little rough but normal throttle seems to be responsive. Here are some videos of my readings.

how old is the rear o2 sensor?

I'm not 100 percent sure but I think I replaced it about 5 years ago