Smeg dishwasher water heating (E3)

Hi,
I have a Smeg STA6143 dishwasher that doesn’t heat the water and is coming up with the corresponding E3 fault code. My Smeg heats water till 65 C (thermometer was on upper basket) about 2 hours, but then corrupts washing and gets fault code E3. I get new water temperature sensor (fitted inside the door). But I’m not sure if it’s really fits for this Smeg (there is no number on this sensor). The problem is in some case resolved and dishwasher is working, but currently the water is about 45 C and the drying isn’t good. So, the question, which part is bad – heating element or water temperature sensor?
Thanks!