Thank you... I'll be doing it the correct way...kickass audio said:The black one is for the data bus signal. That is what triggers the radio to turn on and off. The big harness is the one with the speaker outputs. If you are putting in an aftermarket radio you have 2 adapters you can buy. The cheaper harness if you can find one for GM's that connects to that big gray one for like 15 bucks and requires you to tap into an accessory switchable source to turn the radio on and off with your ignition or you can get the higher end data bus interrupter that retains the factory features like chimes and RAP.