To start with, the Coolant Temperature Sensor uses a thermistor that adjusts its resistance based on temperature changes. This resistance variation directly affects the voltage signal sent from the sensor to the PCM. Problems with the ECT sensor circuits will trigger a diagnostic trouble code. To check the ECT sensor, detach the electrical connector and measure the resistance between the sensor's terminals using an ohmmeter. The resistance should be between 2,500 and 3,000 ohms at room temperature. When the sensor is warmed in water, the resistance should decrease to around 250 to 300 ohms at 180 degrees F. If the test results are incorrect, you will need to replace the ECT sensor. Then replace the sensor, drain about one gallon of coolant, wrap the threads of the new sensor with Teflon sealing tape, disconnect the electrical connector, and detach the old sensor. After that, the installation is the reverse step of the removal process. Finally, you can refill the cooling system.