Unrealistic temperature values

Skoda Ocatvia 1,6 year 2001

My car goes into a emergency mode because of a error in the electronic.

2 ligths i ligthing up in the dashbord, the ASR lamp and System error in the system error lamp (yellow and look like a engine).

The car goes into some kind of emergency mode, It is difficult to start it when it is cold outside and it is not running smoothli.

The workshop tell me that the error code is unrealistic temperature values from the sensor attached to the cooling system.

They have changed the sensor twice, without any success. And they are talking about changing the the engine controller unit, price very high....

When the workshop reset this error, it take 1-2 days and it return and stays on.

I suppose there is a electromechanical device witch regulate the floow trough the cooling system. If there is a error in this device, could that cause a error like a describe.

The cooling fan is running continously when the the error appair.