Suzuki Workshop Service and Repair Manuals

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

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 show such characteristic as shown, replace ECT sensor.