Engine Coolant Temperature Sensor: Description
The engine coolant temperature (ECT) sensor threads into the rear of the cylinder head, next to the camshaft position sensor. (Fig 1). New sensors have sealant applied to the threads.
The ECT Sensor is a Negative Thermal Coefficient (NTC) Sensor. The resistance of the ECT Sensor changes as coolant temperature changes. This results in different input voltages to the PCM. The PCM also uses the ECT Sensor input to operate the radiator cooling fan(s), and send a message over the PCI bus to the instrument cluster for temperature gauge operation.