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

ENGINE COOLANT TEMPERATURE SENSOR-PCM INPUT
The engine coolant temperature sensor is a variable resistor with a range of -40° C to 129° C (-40° F to 265° F).

The engine coolant temperature sensor provides an input voltage to the PCM. As coolant temperature varies, the 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 is also used for cooling fan control.

Engine Coolant Temperature Sensor:

The coolant sensor threads into the top of the thermostat housing. New sensors have sealant applied to the threads.