Engine Coolant Temperature (ECT) Sensor
The engine coolant temperature sensor threads into the water crossover behind the intake manifold. See Fig 1 . The sensor provides an input to the powertrain control module (PCM). As coolant temperature varies, the sensor resistance changes, resulting in a different input voltage to the PCM. Until the engine reaches normal 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.