How a Dishwasher NTC thermistor Sensor works & how to test it
The temperature is controlled by the PCB by means of a NTC thermistor temperature sensor incorporated in the heating element when you test it the Resistance drops as the temperature rises.
What is an NTC Sensor?
A thermistor is essentially a resistor that changes its electrical resistance at varying temperatures. The name is derived from a mix of thermal and resistor. They are used in Dishwasher because their electrical resistance at various temperatures is known, it’s easy for the Dishwasher to monitor a thermistor and detect when certain temperatures are reached.
Check all connections first to the Dishwasher sensor and to the board they may have come loose, you are sometimes unlikely to see anything physically wrong but there might be a bad connection. Diagnosis is done by measuring the resistance with a continuity (or multi) meter. We can’t give readings for all thermistors because they vary, see my picture for an example, but you should be able to get a reading across both terminals. If it’s completely open circuit it’s likely to be faulty.