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.

Fig 1: Checking Resistance Between Sensor Terminals

Courtesy of SUZUKI OF AMERICA CORP.