Engine Coolant Temperature (ECT) Sensor Inspection

Reference: ENGINE COOLANT TEMPERATURE (ECT) SENSOR REMOVAL AND INSTALLATION 

Immerse temperature sensing part of ECT sensor in water and measure resistance between sensor terminals while heating water gradually.

If measured resistance doesn't shown such characteristic as shown in the figure, replace ECT sensor.

Fig 1: Identifying Resistance Between Engine Coolant Temperature Sensor Terminals

Courtesy of SUZUKI OF AMERICA CORP.