It really depends on where the crack is. Take it to a body shop and have them look at it. U really do not want the crack near any suspension related parts. They should be able to weld it for U if they decide if its safe or not. U may have to sign a waiver saying U are OK with this. There won't be any guarantee on the repair because it will probably happen again.

the crack in the frame has nothing to do with the car shutting off ! a good body shop can plate the frame and weld around it and it should hold ! it,s best to plate it then just welding the crack ! but yes a crack can be fixed as long as the frame is not rotted ! after they get it plated then throw some undercoating over the patch and no one will know it,s been fixed unless you tell them !

You might have to have it inspected by your local authority before they will allow it to be road worthy, licensed or sold.

not related, and just weld it up

I have a 2000 Pontiac grand prix gt n majority of my car is new. When they put a new power steering pump in they noticed a crack in my frame. Once this new pump was put in I also have the problem of my car just turning off. Could the 2 be related?