Control circuit for automotive wide band oxygen sensor?

[G-son]

I got a Denso 4 wire oxygen sensor (don't have part number here right now, I'll add it later) for some Subaru in a box of mixed parts, and earlier google searches say it's a wide band sensor, i.e. a sensor that can tell how rich or lean the engine is running, while the cheaper, simpler narrow band sensors just can tell if it's rich or lean, but not by how much. Basically, such a wide band sensor can be a great carburetor tuning aid and if possible I'd like to cobble up a control circuit for it so I can use it.

Does anyone know how control circuits for Denso 4 wire wide band sensors work? It seems 5 wire wide band sensors are more common, but circuits for those probably don't help me much.

Does anyone know how the heater control circuit determines the temperature of the sensor? I know the heater power is PWM regulated, but based on what? I think I've read somewhere that it uses the changing resistance of the heater to tell how hot it is, but I'm not sure and I've been unable to find the source again.

Some info, but I'd like more:
https://www.partinfo.co.uk/files/4%20Wire%20Wide%20Band%20Oxygen%20Sensors.pdf

[G-son]

The sensor is a Denso 22641 AA381, in case that info is helpful to anyone.

[langwadt]

afair( it's many years since I looked into wideband O2 sensors) the temperature is determined by measuring the resistance of the Nernst cell using AC

[G-son]

That does seem correct.

I'm getting a feeling this is a bit too complicated to cobble something up, especially for a sensor I can't seem to find proper data for.