Of course it's connected at the sensor side, but it's not connected at the other side. The sensor wire goes up into the emissions harness, then comes back out on the other side, into an empty plug. It's a small single-wire plug, black in color. The wire color is black and red (brown? hard to tell). Here's the connector, you can also see where it splices into the other harness:
I've been looking through the FSM, at the wiring diagram section, and I don't think it makes sense for this to be a black and red wire, as far as I can tell. Assuming this is the wire for C1-07 (P. Z-44 of the FSM, instrument cluster) it should be solid black. It is up until a certain point, until it becomes this black and red wire. I'm half wondering if this is even the right wire for the job? I know it connects to the coolant level sensor because I tested continuity using a multimeter. Strange.
Anyway...FD owners, could you take a look and see if you can figure out where the hell this thing goes? Trace the coolant level sensor wire back, and it should come out on the other side of the alternator. Also, anyone who wants to come take a look in person is welcome to do so
Thanks!

It's a bit of a trek from speed unfortunately, half hour or so.