Coolant Temperature Sensor/Switch (For Computer): Description and Operation
ENGINE COOLANT TEMPERATURE SENSOR - PCM INPUTFig. 2 Engine Coolant Temperature Sensor:
The engine coolant temperature sensor is an NTC thermistor that threads into the water jacket next to thermostat housing.
The PCM determines engine coolant temperature from the coolant temperature sensor. The ECT sensor is a two wire Negative Thermal Coefficient (NTC) sensor. The PCM sends 5 volts to the sensor and is grounded through the sensor return line. As temperature increases, resistance in the sensor decreases. As coolant temperature varies, the coolant temperature sensor resistance changes resulting in a different voltage value at the PCM engine coolant sense circuit.
When the engine is cold, the PCM will demand slightly richer air-fuel mixtures and higher idle speeds until normal operating temperatures are reached.
The engine coolant sensor input also determines operation of the low and high speed cooling fans.