o2 sensor question

Does anyone here know what wire to the o2 sensor would be referred to as the "signal" wire. There are 2 white wires, 1 black wire, and 1 grey wire...any help would be appriciated.

 

After studying the wiring diagram for an '02 VFR (non-ABS, but I doubt that matters),
I would SWAG that the white wire is the signal wire. I say that because each white one from the sensor(s) traces directly back to the ECM to a discreet pin. The gray wires jumper between each other.

 

you have four wires, 2 white, one grey and one black. the black is the one you want

 

Oh - I see that now, yes you're correct, thanks.