Coolant Temperature Sensor/Switch (For Computer): Description and Operation

DESCRIPTION





The engine coolant temperature sensor is a Negative Temperature Coefficient (NTC) thermistor that threads into the lower intake manifold.

OPERATION
The PCM determines engine coolant temperature from the Engine Coolant Temperature (ECT) sensor. The ECT sensor is a two wire Negative Temperature Coefficient (NTC) sensor. The PCM sends 5 volts to the sensor and is grounded through the sensor ground circuit. 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 temperature 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 temperature sensor input also determines low and high speed cooling fan operation.