Engine Coolant Temperature Sensor
WARNING: This page does not describe the selected car, but rather 33 other vehicles, including the 2002 Saturn Vue, 2002 Pontiac Montana, 2002 Pontiac Aztek, 2002 Oldsmobile Silhouette, and 2002 Oldsmobile Bravada. However, it is still accessible from the selected car via links, so may be relevant.
The Engine Coolant Temperature (ECT) sensor is a thermistor (temperature sensitive resistor). An engine coolant temperature of -40°F (-40°C) produces a high resistance (100 k/ohms), while an engine coolant temperature of 266°F (130°C) produces a low resistance (70 ohms).
PCM supplies a 5-volt reference signal through an internal resistor to ECT sensor and measures return voltage. Voltage is high when coolant temperature is low, and low when coolant temperature is hot. By measuring voltage, PCM can determine engine coolant temperature. Engine coolant temperature affects injector timing and glow plug system.