i know that the target of the discussion is to use the Pico to control the oxygen sensor to broadband, but I think the best way is to use the diagnostic tester with software eobd, in real values, "current pump" where the ECU shows the values in mA, in phases cutoff (much oxygen) or polluting the intake air with exhaust gas, through a tube (little oxygen) I can see if the current rises or falls.
If the sensor reacts I gather that it works, if it is not calibrated is more difficult, but I control through scann tool, long and short adaptation.
With Pico scope I control the heater.
The sensors Bosch possess four wires, but the connector contains a resistance that "transforms" the current signal into voltage signal, to the ECU, in fact the wires are five engine ECU side, on this sensor can be easily measured signal with the oscilloscope, although I think the best way is always the scan tool.
I hope I explained, correct me if I say stupid things.