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

Coolant Temperature Sensor:

PURPOSE
The coolant temperature sensor provides the ECU with information regarding the engine coolant temperature for proper adjustment of injection duration and ignition timing.

LOCATION
Rear of cylinder head, below camshaft sensor.

CONSTRUCTION
The coolant temperature sensor is a Negative Temperature Co-efficient (NTC) type. This means the higher the coolant temperature, the lower the sensor resistance.

OPERATION
The ECU applies constant voltage to the sensor, and monitors the voltage in the circuit. As temperature increases, sensor resistance decreases, causing a decrease in the measured voltage of the circuit. By monitoring the circuit voltage, the ECU calculates the engine temperature and adjusts the air/fuel ratio and ignition timing to meet the specific demands of the engine.