All four of my O2 sensors are randomly and simultaneously dropping to 0.000 to 0.035 volts. When this happens the long term fuel trim spikes to -35%, the car runs like crap, lurches, backfires, etc. Then when the voltage reading returns to normal it runs totally normal.

I got the EWD and checked the ground points, checked the plugs at the ECU, everything is tight. There are so many other components on those same bits of wiring I think there would be a lot of other things wrong if it were a loose connection.

I’m worried the ECU has crapped the bed, but I’d like to somehow confirm that before attempting a replacement. Any tips? Should I open it? What would I look for inside? Can the transponder of a donor key be swapped onto my key blade so I don’t have to replace the ignition cylinder?

 

Given what you are saying about all 4 O2's moving simultaneously this definitely points to a more common issue, ECU? I believe that perhaps some the earliest 1uzfe vvti ECUs of this model possibly suffered the same eventual capacitor failures as the earlier LS400s.
I would start reading how people solved that issue and go from there. Opening up your ECU for a better look could surely verify / discredit this theory. Good Luck!

 

I replaced the EFI fuse and now the whole thing runs better than it ever has. Seems to not only have cleared up the problem but solved my weak shifts between 1 and 2. Who knew such a small thing could cause trouble like that.