Max: My name is Max. My world is fire and blood.
Max: You know, hope is a mistake. If you can't fix what's broken, you'll go insane.
Nux: I live, I die, I live again.
Nux: What a lovely day!
Max: Here they come again... Worming their way into the black matter of my brain. I tell myself, they cannot touch me. They are long dead.
Immortan Joe: Do not, my friends, become addicted to water. It will take hold of you, and you will resent its absence.
Answer: Presumably he is killed. He is attached to the truck with bungee cords and has no protection from the force of impact in the crash, which is sufficient to break the rig into pieces. There is no way he could have survived the crash.