What do you mean by "reversing polarity for cross testing" Are you saying that when you reverse the probes you get a different resistance reading? The thermistor should read the same regardless of which probe is on which connection.

If you believe that the sensor is bad then you could hook up a resistor of what ever value it is supposed to be at running temp and if the engine is at running temp then it should be happy. I don't think zero ohms would be a good idea.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra