940 Non-turbo

After reading the 900 FAQ and the archive on O2 tests, I am getting a little confused over the wiring colors.

My O2 sensor has a pigtail that ends in a single terminator with three wires - 2 white and one black, although there are four spades coming out of the terminator.
The black connects to the green wire of the terminator that goes to the ECU, while the two whites goes to the two whites of the ECU terminator.

All the tests mentioned in the archive and the 900 FAQ refer to the green wire for voltage test. Also the two white wires, which I presumed is to provide the voltage for the sensor heater must be plugged in.

Since mine comes in a single terminator it is impossible to plug the two white wires without also plugging in the black to the green. I read that voltage fluctuations should be read from either of these black or green wire. I assume I should read from the black and not the green, while the remaining two white wires must be plugged in at the same time.

Can some one tell me how to go about with testing sensors with one terminator and three wires?

O2 sensor is costly and I do not want to change if it is not necessary. BTW I've the lambda light on the dash and got a code 2-1-2. I've changed the sensor with a previously working unit but the lambda stayed on after I've cleared the codes several times.


Laozong