How do you ask What is wrong in French?

What's wrong? --> Qu'est-ce qu'il y a ? -- "kess keel yah"

This expression, which literally means "what is there?", is very common and is always understood to mean "what's wrong?" when not followed by anything else. You could make it more formal by using inversion: Qu'y a-t-il ? ("kee ah teel")