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

Engine Coolant Temperature Sensor Location:

DESCRIPTION
The Engine Coolant Temperature (ECT) sensor is a thermistor (a variable resistor that changes along with temperature changes) in series with a fixed resistor in the Engine Control Module (ECM) that measures the temperature of the engine coolant.

OPERATION
The ECM applies 5 volts to the ECT sensor. The ECM monitors the voltage across the ECT sensor and converts it into a temperature reading. When the engine is cold the ECT sensor resistance is high, and when the engine temperature is warm the ECT sensor resistance is low. Therefore, when the engine is cold the ECM will receive a high voltage input, and when the engine is warm the ECM will receive a low voltage input. The ECT sensor is located on the RH side of the intake manifold.