What is wrong with my vehicle? I get a fault notice that left turn signal light is broke. However the turn signal lights all work fine. It´s the notice system that is bust. What can I do?
Take it to the Benz dealer and tell them the problem you are having. It may be software, it may be hardware, there is no way for a group of even knowledgeable folks on the internet to know for sure.
Be prepared to pay a diagnostic fee. And because it is Mercedes Benz, it will be a large bill. It will take some work to determine what is causing this and the tech deserves to be paid. You want it fixed the first time, right?
If these are incandescent bulbs, it would be cheap to replace all of them first just to make sure they all have good filaments and good electrical contact.