Need o2 sensor help (down-stream)

[ninety1two40]

@offroadzj

not sure if it helps at all, but its a 4 wire sensor. 2 white (heater), gray, and black. So if it is + on simulator/sensor and - on chassis, is gray or black the +?? I am good when it comes to electrical, but I dont have an idea in the world how an o2 sensor works… lol

Put your meter’s red lead on the gray and the black lead on the black.