Engine Coolant Temperature (ECT) Sensor
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The Engine Coolant Temperature (ECT) sensor is used to sense engine coolant temperature. The sensor protrudes into the thermostat housing. The ECT sensor is a two-wire Negative Thermal Coefficient (NTC) sensor. Meaning, as engine coolant temperature increases, resistance (voltage) in the sensor decreases. As temperature decreases, resistance (voltage) in the sensor increases. At key-on, the PCM sends out a regulated 5 volt signal to the ECT sensor. The PCM then monitors the signal as it passes through the ECT sensor to the sensor ground (sensor return). When the engine is cold, the PCM will operate in Open Loop cycle. It will demand slightly richer air-fuel mixtures and higher idle speeds. This is done until normal operating temperatures are reached.
The pressurized coolant bottle is mounted on top of the radiator. The coolant recovery/overflow bottle is made of high temperature plastic. The radiator overflow hose and the bypass hose connects to the top of bottle in order to help get trapped air out of the coolant system. Coolant is drawn back into the engine through the lower hose.