The temp sensors are what is called a NTC (negative temperature coefficient) thermistor (thermal resistor). Big fancy way of saying the change their resistance value opposite what the temp around them is doing. Very cold = high resistance, very hot = low resistance. -37 is the default cold setting indicating the highest possible resistance to current flow. This can be caused by a bad wire, connection/connector, or a bad sensor. You can test it by putting a digital multi meter on it (the sensor, out of the car) in the ohm setting (omega symbol). You should get a value, then pass it near a flame or heat source (warm it up) and the reading should go down. If so, the sensor itself is most likely good and you need to check the wires (you'll need a schematic for that). Otherwise get a new sensor, plug it in and see what happens. Oppositely if it reads like +174 all the time you have a short most likely bypassing the sensor. Stuff not being plugged in unfortunately happens a lot when things apparently stop working (it's just easier than fixing it in most cases. Sometimes its ok, but more often than not it causes other unforeseen problems that can really bite you in the butt. I'll tell you several stories about some of my various "ok crap that's what that does" stories sometimes :-).