hey guys i need your help, my stock O2 sensor was eaten up which looks like a rat or something so i went to the local boneyard and found the 4 wire O2 sensor i need only problem was the engine had front end damage and i had no choice and limited tools on hand so i cut the wires. so now im at home and i cant figure out which heater wire is which. i looked in my helms and it only shows which is which if your looking at the plug not the O2 sensor itself and my stock one was cut also cause i tried to repair it but that was immpossible.

all i need to know is when you look at the wires coming out of the O2 sensor in this sequence black-green-black-white i just need to know which black is positive and which is negative for the heating element inside on the O2 sensor itself.

thanks