European O2 wiring K20A

[JavanR1]

Hi, Can anyone tell me how to wire in a european narrowband O2 sensor (the front one only) to a PRA K-PRO? There does not seem to be much info on this. I have read that it wires direct to the ECU and does not go through a relay. The engine is not in a Honda.
The O2 has 4 wires
White
White
Black
Grey

I think the white wires are heater, but I need to know which one is + and - on the other two.
I hope someone can help as I just keep getting conflicting info.