Review on Buick Chevy GMC Pontiac Car Stereo Radio Wiring Harness with Antenna Adapter by Geoff Yates

The 2004 Chevy Trailblazer (not Onstar) did not have a keyed power wire in the available accessory location where the factory radio is located, or in the factory wiring harness. Thus, the cable in the plug is connected to air, since there is no mating pin in the factory wiring harness. So you need to find a power adapter with a key on the cord to plug it in. I found mine in a large factory plug that was under the steering column and routed a broken piece of wire to my new radio to provide power when the key was on to power the secondary radio. Just a cable and instructions would have made this 5 star adapter last all day. It fitted the factory plug perfectly and all other cables for the speakers and DC power were correct. The radio antenna adapter also worked great for my application.