O2 Sensor - Only 2 Wires Connected?

[Ben Swann]

[1987 5kCSTQ Avant

Was checking my O2 sensor today and saw that only the two white wires are
plugged into a connector. The black wire has a boot and male flat connector,
but it isn't plugged into anything. The only other unused compatible female
connector is located near the fuel filter toward the firewall. Anybody know
if this is the way it is supposed to be? ]

[I thought the whites were for heating, and the black was for signal?] <--That is correct

If it was unplugged intentionally, it may have been that the sensor had gone bad which can cause the engine to run miserably and die when the engine goes into closed loop mode.  I have had this happen on several cars.  Unplugging the sensor let the engine run fine until I could replace the sensor.

Ben