On star, amp?
 

https://cimg2.ibsrv.net/gimg/chevrol...c80e85b8b3.jpg
What is this it? It's made by LG model number TC96GAJ. I Google it and it didn't come up with anything useful.

It's the communication module. Does GPS, cell, satellite

Is it just for Onstar. I just a have a CD player without navigation. Is the yellow plug supposed to be connected to it.

OnStar. Satellite radio.gps navigation. Probably car phone.

Despite a lack of a navigation head unit, GPS is an integral part of any cell phone Since the mid 90s. In case of an accident, an OnStar operator would need to know where you are. And even if you don't subscribe to OnStar, it has the ability to call 911. This is true of any cell phone.