If you look at the wiring diagram and the engine wiring harness, you'll notice there are 6 wires for the Upstream O2 sensor (wideband) on the N series engines.

However, the Bosch and NTK sensors have 6 pins but only 5 wires. Does anybody out there have a genuine MINI O2 sensor that could report how many wires on coming out of their sensor? I'm wondering if the Bosch and NTK sensor are sharing a ground or power inside the sensor connector.

Here's a pic from the wiring diagram.

 

Well, I think I figured it out. It's ok to have a 5 wire sensor plugged into a 6 wire harness. "To save wires, the Vs (sense) and the Ip (pump) cells are connected together - they share a common reaction surface anyway, so this isn't a problem."

https://wbo2.com/lsu/lsuworks.htm

I've updated the MINI schematic to go along with the above theory of operation link above.



Next step it to get my multi-meter out and check to make sure I got it right.

 

Ah haaaa!

Go to the 30 minute mark in the video.