You're either not listening or you're not describing things well... the GTE's O2 sensor does NOT have just one wire!
From Toyota's service manual the O2 connector will have:
Red w/ blue stripe (HT ground signal)
Black w/ red stripe (HT power)
White (OX signal)
Sounds like yours is just discolored. Post pics of the connector and we'll know for sure.
No idea what the other connector (with the Yellow and white/blk wires) you're trying to describe is... post pics and location.
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