I've been through some diagrams for your car on Autozone.com and on my Service Manual even though is for 1998 Contours.
I'm not sure about what polarity are you asking here, because the ECT is a variable resistor input to the PCM, so there isn't polarity as I understand it.
Anyway, the ECT wires run between the PCM on pin 7 with the White/Green wire. The Brown/Green wire splices over with other components like the Intake Air Temp Sensor, EGR Sensor and others. That splice ends on pin 46 of the PCM with a Brown wire.
You can look for continuity between pin 46 and your Brown/Green wire on the ECT and between pin 7 and your White/Green wire. Between pin 7 and 46 you should get some resistance that varies with the engine temp.
Yes there are some connectors in the middle but can't be sure about it because my service manual is for the 1998 Contour.
The service manual states that White wires are Sensor circuits and Brown wires are sensor signal returns (reference/ground).
Hope this helps you troubleshooting your problem.
