Just to expand on what has been mentioned.
Engine Coolant Temperature (ECT) sensor 1 is mounted in the rear crossover pipes.
Sensor 2 is in the lower hose at the thermostat.
The thermostat has a heater that allows the PCM to control the opening function.
The electric thermostat has 4 connections. The lower connection receives coolant from the radiator lower hose and the ATF cooler. The larger upper connection is connected via a hose, water supply tube and water outlet to the cylinder block. The flow from this connection is governed by the thermostat. A connection at the side provides flow to the coolant pump and a smaller connection from this receives coolant return from the heater core and the coolant expansion tank.
The thermostat begins to open at 208-215 °F and is fully open at 226 °F.