Does anyone know what this sensor is ?

[Seanie280672]

as the title suggests, does anyone know what this sensor is, its a black plug with 1 wire only, it plugs into a brass looking sensor which screws directly into the head in-between the vacuum pump and the thermostat housing, it appears to be there all on it own.

I broke the plug on it whilst fitting a new vaccum pump a few days ago and want to see if I can just purchase the plug rather than a whole new wiring loom.

 

[Nichebenice]

Could be some kind of o2 sensor, maybe an air heat sensor/regulator?
Just basing that on the description, to me that just looks like a lead plug.
What car, and can you show the end of the sensor?