On most vehicles, the coolant temperature sensor (CTS) can be found somewhere near the engine thermostat, which allows it to function optimally. The tip of the CTS is probably located right next to the engine coolant.
The sensor works by measuring the temperature that’s being given off by the thermostat and/or the coolant itself. The temperature is then sent to the on-board control system. From there, your vehicle’s computer will use this temperature information to either continue operating or adjust certain engine functions, always working to keep the engine temperature at an ideal level.
As the control system receives the temperature from the CTS, it may trigger the cooling fan to either shut off or turn on. Additionally, it may signal the need for a richer fuel mixture or open the exhaust gas recirculation.