Is Theft module bad?

I replaced starter,soliniod,ignition switch,battery,body control module..key relearned.dealership said old bcm was fried .so I bought a new GM bcm module.turn key clicks once .i got lights .no dash lights except security but it goes out when turn key.radio reads blocked.

With a security system problem your best bet is the Dealer. All the relearn, reset, etc. procedures that everyone talks about will not work for 99% of security system failures. Those procedures are to be used as part of a specific repair to the security system. It will be cheaper in the long run to let your local Chevrolet Dealer fix it. Hope that helps! Jim