The 4 pin B11/2 sensor is actually 2 sensors in one case .. They should both read the same ..they are internally wired diagonally opposed , so any diag set of pins gets you one resistor measure. That would be pins 1/3 or 2/4. You are looking for 2.5K ohms at room temp [ 20C] or 325 ohms at coolant running temp of 80C.
This is a thermistor , so that is why there is a temp/ohms variable ..decreasing resistance as temp increases [ Neg Coefficent Thermistor,,, NCT].
That is if you have the 4 pin...these two sensors are electically isolated from each other, so you can not get a double resistance value from this 4 pin sensor ,,

If you have the two pin , [ which you do, if I am reading your post correctly]then each resistor is internally wired from one pin to ground, so each will be the same if you test across each pin to ground individually. If you just go across the two pins , you will get double the resistance b/c each resistor shares the same ground, so you would then be actually reading two resistors in series across the two pins. [ R1 + R2 ..ie....double the resistance of each individual resistor.]
Your chassi can have either sensor , depending on chassis #..
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