The engine coolant temperature sensor resistance changes in response to engine coolant temperature. The sensor resistance decreases as the surrounding temperature increases. This provides a reference signal to the PCM, which indicates engine coolant temperature.
The ECT sensor is mounted on the lower intake manifold near the water outlet/thermostat housing, except on 2.3L and 2.5L engines. On the 2.3L and 2.5L engine the ECT is mounted on the water outlet/thermostat housing.
The coolant temperature sensor is a variable resistor that is influenced by temperature. Which means, as the temperature changes, so does the resistance inside the sensor. The computer reads this change in resistance to determine the operating temperature of the engine. It uses this reading to determine proper air/fuel mixture and ignition timing settings.