A couple days ago, I got this annoying error of “Nozzle is too higherature” on my Ender-3 V2 and tried to fix it. I disconnected the thermistor from the circuit board and turned it on, but the same error occurred, so I decided that the error must lie somewhere within the circuit board, but when visually inspecting the board, nothing seemed burned or damaged. I am unsure whether or not this issue has been encountered by someone else; however, I would greatly appreciate any assistance that you could offer.
Do you have a multimeter?
What does the printer show for the hotend temperature when it’s at room temperature?
If it’s showing values that are not plausible you could measure if the thermistor has about 100kΩ at room temperature. If it has then it’s likely a problem with the board.
I’ve had this issue before when running without the silicon ‘sock’ around the hotend. Refitting it fixed the issue.