Unless your car is still under warranty, there is no way you should be taking it to that dealer. In any case I would guess the dealer has read the codes and you should ask them to tell you exactly what the codes were. They likely will be something like “P1234.”
If it is not under warranty stop paying an apparently incompetent dealer big dollars to not fix it. Find a recommended local [b]independent[/b] mechanic.
We need to know what those codes are before starting on this on.