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

Engine Coolant Temperature Sensor:

The Engine Coolant Temperature (ECT) Sensor is located in the coolant pipe attached to the cylinder head (# 2 in image).

The engine coolant temperature sensor is an NTC resistor. The electrical resistance of the sensor decreases as coolant temperature increases. The engine coolant temperature signal is used by the Motronic control module for ignition timing, idle speed control and fuel injection quantity.

In addition, various functions such as oxygen sensor control, deceleration fuel shut-off and evaporative emission system operations are based on output from the engine coolant temperature sensor.