Engine Coolant Temperature (ECT) Sensor Inspection
WARNING: This page is about a different car, the 2008 Suzuki Grand Vitara, 2007 Suzuki Grand Vitara, and 2006 Suzuki Grand Vitara. However, it is still accessible from the selected car via links, so may be relevant.
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 show characteristics as shown in the figure, replace ECT sensor.