fanzo Professional Electronics Expert Team

It's a thermistor error, the internal evaporator one... but disconnect the fridge and freezer ones first in turn to see if the error changes. If it is the internal one, you should see an arrow impression on the paper covering the insulation which marks the spot to dig(at the back of the freezer.) Usually this error occur when water ingresses the push on tags, shorting out the thermistor.

Now the bonus... 9 times out of 10, you don't need to buy a spare, as there will probably be nothing wrong with the error giving thermistor. Remove and fit the fridge thermistor in the place of the internal one... clean and dry the internal one you removed and refit it inside the fridge.

You will need to repair the insulation with two pack brown foam insulation and foil tape.
Good luck