Using Multi-Meter

Remove the engine coolant temperature sensor from the intake manifold.
With the temperature sensing portion of the engine coolant temperature sensor immersed in hot engine coolant, check the resistance.

Fig 1: ECT Sensor Check Item Table Using Multi-Meter
Courtesy of HYUNDAI MOTOR CO.

Fig 2: Checking ECT Sensor
Courtesy of HYUNDAI MOTOR CO.
If the resistance deviates from the standard value greatly, replace the sensor.

Fig 3: Resistance Specification Graph
Courtesy of HYUNDAI MOTOR CO.