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

Fig. 14 Engine Coolant Temperature Sensor:

OPERATION
The Engine Coolant Temperature (ECT) sensor has one element. The element supplies coolant temperature signal to the PCM. The PCM supplies coolant temperature information on the CCD bus to the Body Control Module (BCM) for the instrument panel gauge cluster. The PCM determines engine coolant temperature from the coolant temperature sensor.

As coolant temperature varies, the ECT sensor resistance changes resulting in a different input voltage to the PCM.

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 ECT sensor threads into the intake manifold next to the coolant fill neck/thermostat housing Fig. 14. New sensors have sealant applied to the threads.