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

ENGINE COOLANT TEMPERATURE SENSOR - PCM INPUT

Fig. 2 Engine Coolant Temperature Sensor:

The engine coolant temperature sensor threads into the front of the driver side cylinder head.

The PCM determines engine coolant temperature from the coolant temperature sensor. The ECT sensor is a two wire Negative Thermal Co-efficient (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.

Until the engine reaches operating temperature, the PCM demands slightly richer air-fuel mixtures and higher idle speeds.

This sensor is also used for cooling fan control and A/C cutoff at high coolant temperatures.

This 3-way sensor is also used for the water temperature gauge and dashboard warning light.