Good question Steve! If there was a coolant sensor and it was unplugged, the gauge wouldn't work

I'm pretty sure the law was passed in 1995 to make all cars OBDII and all 96's on up should be OBDII. I suppose it's possible that half of the 96's could be OBDI still... hell half of the 96's have weird parts on them to begin with!

I thought you might be talking about the INTAKE temp sensor, but that's supposed to be in the intake manifold and not screwed into the head.

Is your check engine light on?