Ender 3 temperature stuck at 150

Hi I have an ender 3 with which I printed then one day the temperature started to display 150 without stopping even at start-up whether the nozzle was cold or hot, so I could not print and if I started preheating the temperature does not move and smoke emerges from my nozzle even without introducing the pla.

I tried to change the thermistor and the heater cartbridge several times but the problem persists, do you know what I could have done wrong?

Thank you for your answers