Using Multi Meter

With the temperature sensing portion of Water Temperature Sensor (WTS) immersed in hot engine coolant, check the resistance.

Fig 1: Illustrating WTS Resistance Chart
Courtesy of KIA MOTORS AMERICA, INC.

Fig 2: Testing WTS Resistance
Courtesy of KIA MOTORS AMERICA, INC.
If the resistance deviates from the standard value greatly, replace the sensor.