Oxygen sensor wires
 

I need the wires of a 2009 mazda 3 oxygen identified by what each color does.
I have 5 wires: Black, White, Blue, Red, and gray. I know the red usually is power from the ignition; Black usually is ground. and I believe the white is for heat.
I'm looking for the wire that sends the signal from the O2 sensor to the computer.
Can anyone help me, Please!