At least on my car, here were the voltage readouts ..
White wire 2.5v black wire .02v
gray wire 0v white wire 12v
since the circuit was never closed, the ground had no voltage (gray) signal will be less than 1v the two wires are heater wires, I believe one gets switched from 2.5 to 12v and the other is a constant 12v (heater wire)