Engine - Coolant Temperature Sensor/Switch: Description and Operation

OPERATION
The engine coolant temperature sensor provides an input to the Powertrain Control Module (PCM). As coolant temperature varies, the engine coolant temperature 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 engine coolant sensor input also determines operation of the radiator fan.