Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection

ENGINE COOLANT TEMPERATURE SENSOR (ECT SENSOR)

The engine coolant temperature sensor is located in the engine coolant passage of the cylinder head. It detects the engine coolant temperature and relays signals to the ECM. It employs a thermistor which is sensitive to changes in temperature. The electric resistance of a thermistor decreases in response to temperature increase. The ECM judges engine coolant temperature by the sensor output voltage and provides optimum fuel enrichment when the engine is cold.

Circuit Diagram:

Using Hi-scan:

Harness Inspection Procedure:

SENSOR INSPECTION
1. Remove the engine coolant temperature sensor from the intake manifold.




2. With the temperature sensing portion of the engine coolant temperature sensor immersed in hot water, check resistance.




3. If the resistance greatly deviates from the standard value, replace the sensor.

INSTALLATION
1. Apply sealant LOCTITE 962T or equivalent to threaded portion.
2. Install engine coolant temperature sensor and tighten it to specified torque.

Tightening torque
Engine coolant temperature sensor
SOHC:15 - 20 Nm (150 - 200 kg.cm, 11 - 15 lb.ft)
DOHC:25 - 30 Nm (250 - 300 kg.cm, 18 - 22 lb.ft)

3. Connect the harness connector securely.