I recently purchased an amp, I have onstar. My harness to the factory amp had been disconnected. I spent $870.00 to have this work done. I had to go to Best Buy and have the new amp uninstalled. It cost me $380.00 to get all the factory options back to normal. Be careful about who u let work on you're car. I wanted an after market amp on the factory radio a litlte more volume. Second amp was disconnected and now just have one on my 2 12" in the trunk. Bummer for me.