ECT Sensor

Range 0-5 Volts:
The Engine Coolant Temperature (ECT) sensor sends a signal to the PCM relative to engine coolant temperature. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the PCM monitors a high signal voltage and interprets it as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal will decrease and the PCM will interpret the lower voltage as a warm engine.