does anyone know what it is for?? because mine is not pluged in (ED 6cyl)

a pic would help?

there is a sensor on the rear of the thermostat housing which has something to do with the climate controle ..if your car doesnt have electronic climate controle it wont be used..
but the ones i have seen are blue..
the large one closest to the front is the coolant temp sensor for the ecu.
and the small round one is for temp guage.

on my ED xr6 there is no sensor there, instead there is a water outlet that goes to the LPG convertor....I was trying to find out why I had a blue plug not connected to anything, so I had a look on a ED fairmont and it had the blue plug going to a yellow sensor on the thermostat...

I just wondering what would have been in its place before they put the water fitting there.