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

Engine Coolant Temperature Sensor:

PURPOSE
The engine coolant temperature sensor provides the ECM with information regarding the engine temperature necessary for proper adjustment of injection duration.

LOCATION
On intake manifold flange, between cylinders 2 and 3.

DESIGN
The coolant temperature sensor is an NTC (negative temperature coefficient) type. This means the higher the coolant temperature, the lower the sensor resistance.

OPERATION
The ECM applies a regulated constant voltage to the sensor, and monitors the voltage in the circuit. As temperature increases, sensor resistance decreases, causing a increase in the measured voltage of the circuit. By monitoring the circuit voltage, the ECM can calculate the engine temperature, and adjust the air/fuel ratio and ignition timing to meet the specific demands of the engine, at that temperature.