Sorry to revive an old thread, but I discovered how to make the radio function outside of the car and I thought I would share it with anyone still searching for this. I used the bcm; however, I only had to connect 3 wires from the bcm (power, ground, and the gmlan) to make the radio stop displaying "security lockout active" which makes me believe that it would be somewhat simple to make a device that would mimic the bcm. This is for the radio function only, I have no idea how you would make the hvac work also. Take out the bcm (from the same car that the radio came from) and the blue plug that connects to it. (Hopefully you have a wrecked car like I do that you can just tear out the radio and bcm with no regrets.) Connect the orange wire with a red stripe to 12v, the black wire at the top left of the connector to ground and dark green wire at the top right of the connector to the gmlan on the radio. The radio should now function properly.