Coolant temp sensor

Does any body know the actual job of the coolant temp senasor, the 2 wire jobby screwed into the thermostat housing, if unplugged throws a light, but thats it, i am trying to get my engine to rev higher when cold is this sensor also connected to the ecu to feed coolant temp as well as the dash temp.

There are two sensors mounted in the thermostat housing, the two wire (white on diesel) one is for the temp guage, the three wire (green on diesel) one for the ECU. They have an extra wire to "usual" as the thermostat housing is moulded out of (rather rubbish) plastic, so they need an earth. Why do you want to rev your car hard when cold?

There are two sensors mounted in the thermostat housing, the two wire (white on diesel) one is for the temp guage, the three wire (green on diesel) one for the ECU. They have an extra wire to "usual" as the thermostat housing is moulded out of (rather rubbish) plastic, so they need an earth. Why do you want to rev your car hard when cold? EDIT - checked you posts and se its idling low when cold. OK. makes sense now!

Yes soz i just want the idle to raise ie choke when cold, just checking the sensor is not in open loop and if it sends a signal to ecu to open idle air valve. as i mentioned in previous post my t4 idles very low on cold starts