Yes Hello i can confirm that this works by splicing into the onstar harness mic wires, however mine is an 04 chevy silverado & in 2004 their mic technology wasnt that great,this mic was only meant to talk to onstar for an emergency so the mic quality is horrible. everyone says that they cant hear me when im driving and its just poor quality so i suggest buying an aftermarket mic and replacing the old one!Hello bfisher1157... Are you still around? I was hoping to pick your brain on this topic of tapping into the OEM OnStar mic and connecting it to the rear microphone port on my aftermarket radio. I want to do this on my 2005 GMC Sierra 1500 HD pickup. Looks like you were able to do it on your vehicle. Please advise. THANKS!