Toyota Sienna 2008 V6 3.5L, P0158

I checked the wiring it is not rubbing anything and the OBDII real time readings seem sane, but differ between bank1 and bank2. The seeming slugish-ness of the bank2/s2 is suspicious (and also confirmed by the ECU error code P0158). It seems to linger in the high voltage range (around 0.8V) but it's not like it never responds: after high rev and release, it drops to 0 just like bank1/s2, but then bounces back a lot sooner than bank1 sensor 2. I have ruled out bad contact/wiring issue as it's consistently behaving the way it does and by visual inspection. Unfortunately I have not first observed behaviour of the original sensor before replacing it, but at this point I have no reason to believe the original sensor was bad at all. When P0158 came on, I had another error code about small evap leak. Unfortunately, I ruled that one out and never looked into it in more detail. It takes some time before EVAP self test runs again, but researching on the net it seems that evap issues may express themselves in the over-rich mixture and such. Though, I have hard time correlating that with only bank2 rich mixture (I would expect symmetrical effect on both banks)

Short term trim swings from -20% to +5% which is very similar on both banks. Long term trim on bank 2 is different than B1. On b2 I get from +4.7% to +7% In contrast, on bank 1 it’s between -2.7% and +4.7%

just an update to those who might stumble upon this: DO NOT REPLACE your O2 sensor before you have tested A/F sensor heater resistance. In my case it turned out to be upstream (A/F sensor) - heater circuit was open. Note that OBD did read A/F sensor reaction but it was always a bit offset compared to Bank1 (good bank). Replaced A/F sensor, and after a short drive, ECM performed all tests and all is good.