Arguments for God's Existence from Contingency

[brewer]

I prefer discussing the modern version of the Argument from Contingency:

1. Everything that exists has an explanation of its existence (either in the necessity of its own nature or in an external cause).
2. If the universe has an explanation of its existence, that explanation is God.
3. The universe exists.
4. The universe has an explanation of its existence. (from 1 and 3)
5. Therefore, the explanation of the universe’s existence is God. (from 2 and 4)

It is easier for someone to understand right away. Aquinas' takes getting used to the language and the various threads of logic. 

So, which of these premises are wrong?

1, 2, and 5.