What are the consequences if you are in a chapter 13 and you sell your house without getting approval from the trustee?

You can't. You would not be able to obtain a clear title. And even attempting such an action, would be a very foolish thing to do. The 13, would be in default and dismissed. Your creditors would be on you like "ugly on ape". And, trust me, you really don't want to hear the rest.....