A couple of questions on the 3 wire sensor. ('88 2.1 L).  If I understand
this thing, the two white wires are to heat the O2 sensor, and the polarity
is not important... Right? Now, that leaves the black wire to be connected to
the fat green wire. Is that the signal wire, or is it a ground wire??
Secondly, does the wire have to be sheilded?

Thanks - Brian Doss