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

Coolant Temperature Sensor (CTS):

LOCATION

The coolant temperature sensor is installed in the coolant passage that runs across the front of the intake manifold.


FUNCTION

The sensor element extends into the coolant passage where it maintains constant contact with the engine coolant. The engine controller uses this sensor to measure the temperature of engine coolant.


OPERATION

The engine controller sends out a reference voltage of approximately five (5) volts to the coolant temperature sensor. As coolant temperature changes, the internal resistance of the sensor will change, causing a varying voltage drop across the sensor. The engine controller reads the voltage drop across the sensor as engine coolant temperature.

Based on the amount of voltage drop at the coolant sensor, the engine controller will, adjust the fuel injector pulse width (a cold engine will receive a longer pulse width, allowing for a richer mixture), compensate for condensation of fuel in the intake manifold, monitor and adjust engine warm-up speed, advance ignition timing when the engine is cold, and activate the Electric EGR Transducer (EET) to prevent vacuum from reaching the EGR valve.