two wires are for the heater circuit and the other two are for the signal. If there is a red with black stripe wire on the driver side o2 harness then that is the signal wire to the pcm. The grenn and black wire is the ground.
If its like the 99 cobra's o2 sensor, you have 2 whites, 1 gray, and a black. You need to use the black wire on the o2 which will connect to the purple wire comming out of the autometer gauge(if thats the one your using) Hope this helps, I had to just try wires till I got it right on my car. I tried the gray first and that was definatly not right!
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