What is this module/sensor?

It's on the passenger side of the radiator, toward the top side. 99 SS M6.
I was doing some surface rust abatement from a previously leaky battery and came across an unplugged and fuckered up pigtail, no doubt coming from that module.
Ah the joys of other people's former cars.....
Thanks for any help.
Most every other sensor on modern cars trips a light when the sensor fails. The second the wire was cut, the dash should have signaled low coolant.
Maybe a bulb is out back there....








