Thread: 2008 Grand Prix Question

If you have the 2 white plugs that would go to the onstar module up inside the dash it will be very easy. Just look under the center of the dash ahead of the center console and you will see them if you got em. Just above where the wiring harness goes to the center console.
If you got those two connectors you may even have the antenna wiring as well.

I added it from scratch on my 04 by changing out the dash harness while i was adding other options and could not get onstar to recognize my car as it really was since the module was from a wrecked car, however im sure if you get higher up tecnical at onstar or maybe the dealer reflash the onstar module you can get it to match your vin and everything. Just my 04 ended up getting wrecked so i nveer got that far.

the wire's are up in the ceiling by the rearview mirror, evidence that there was the mirror there.

I wouldnt say it was there, Just it was left out at the assembly line, you can confirm this by looking at the service parts label under the carpet/spare tire cover. If you have RPO code UE1 it did have it, if you dont have this code and have something like UE0 or similiar it was left out to begin with.

All roofharnesses that had the lamp group option that included the rear interior lamps with switches automatically come with the plug just up inside the headliner.

You have the headliner harness for onstar which you confirmed, The body harness already has the onstar wires in it already since i know they do from experience, so now the last thing to confirm is if the dash harness has the wires which is why we need to know if those two plugs exist under there.

Let us know what you find

If you have these two plugs you will need mainly the onstar module, mirror, and antenna. For the antenna you will have to make the mounting holes in the roof to accept the antenna unless you have an xm antenna which case there would already be holes and just need to swap the antenna.