Just recently got my 2001 Blazer back up and running after a totally ignition system replacement (coil, module, cap, rotor, wires, plugs) and cat replacement. So everything good, passed emissions and no codes. BUT while monitoring the engine through live datalogging, I notice that while the throttle and load are steady, one bank's O2 sensor voltage varies from about .5 to .78 volts with no fuel trims while the other bank's O2 jumps wildly from .1 to .9 volts (with more time spent around .7 to .8 and fuel trims are about 3-6%.
Again, nothing really bad, but it does cause a slight stumble. My best guess is a leaky or poorly flowing injector which would explain the rich condition numbers and why it's only on one bank. I do run fuel system cleaner semi regularly, but it was sitting for a while before I made the time to get it fixed.
Any other ideas?

**before​before the "15" was an open throttle event where it leaned out, overcompensated, then sloped back down closer to stoichiometry**

 

Bank 1 sensor 2 is post-cat converter.

You need to monitor bank 1 sensor 1 and bank 2 sensor 1 to see both banks. As long as both are cycling back and forth across 0.45V, they are controlling the fuel mix. Post cat converter O2 sensor should be much steadier without the same cycling frequency as the upstream sensors.

I'm thinking you are just fine, and what you are observing is quite normal.

 

Ahhh, I see what I did.. had a dyslexic moment thinking the b1s2 was b2s1😝