I need to connect my o2 sensor without the factory connection. It took a long time to find the information on what the wires do and now I need help telling which wire connects where. There are 4 wires on the o2 sensor a black wire for the signal, a gray wire for ground and 2 white wires for the heater. Here is the wirind diagram for the car's harness. The car is a 92 325i. I would really appreciate any help on which wire from the harness connects to which wire from the o2 sensor.