Car shown is 1 8t skoda octavia vrs same par.
Audi a4 coolant temp sensor location.
You can always detect a bad coolant temperature sensor by reading the engine diagnostic code but you can also detect it by the increase in fuel consumption the sudden change in the temperature gauge or by seeing black smoke coming out of.
Here is a quick video on how to replace a temperature sensor on an audi a6 with a 2 8l engine.