Circuit Description
WARNING: This page is about a different car, the 2000 Saturn LW2 and 2000 Saturn LS2. However, it is still accessible from the selected car via links, so may be relevant.
Engine Coolant Temperature (ECT) sensor is a thermistor (resistance changes as engine coolant temperature changes). ECM supplies a 5-volt reference voltage to ECT sensor. As temperature changes, ECT sensor resistance changes, which changes voltage.
As coolant temperature decreases, ECT sensor resistance increases. As coolant temperature increases, ECT sensor resistance decreases. ECM monitors voltage input from ECT sensor and converts it into a temperature value. DTC will set when signal being received deviates more than 7°F (12°C) from ECM modeled temperature. ECM continuously calculates this modeled temperature using ECT starting temperature, MAP, MAF and engine run time.