I just purchased a 2007 Grand Prix GXP. It has a stock Monsoon CD Player w/XM. Car also has Onstar but I'm not subscribed and no plans to.
I'm going to install a Pioneer Avic-Z2 Nav head unit with all the options. I have all the info I need for using the stock XM antenna so I don't have to install another XM antenna for the after market unit.
My question is, can I use the stock GPS antenna from the onstar unit for my Pioneer Avic-Z2?
I have read a few forums that say I can and a few that say I can't. Does anyone have a definitive answer.

Note this: I had a Circuit City installer tell me he couldn't install any after market HU while still using the stock speakers & Monsoon amp. He said it would burn up the Monsoon amp. He said I would have to install all new speakers and ditch the amp. He also said I would never get an after market HU to sound as good as the stock system. I don't know if he was that stupid or if he thought I was that stupid. Needless to say, I walked away and will never go back. Also, every installer I talked to said I couldn't use the stock XM antenna and wanted me to purchase one. I have since learned otherwise.

you can install a aftermarket cd player w/ the monsoon. You just have to tie into the stock amp turn on from the aftermarket head unit, and a few other things. I wrote a write up on it a lil' while ago, I am a lil' busy right now, but will post a link so.

You can use the stock gps antenna for the avic, but it requires a a lil' bit of electronics experience. It is just easier to put the new antenna in.

__________________
Steven Oliver
2004 GTP comp-g WS6. Gator and suede all around interior.
Advanced MECP certified installer, custom upholsterer.

I know I can use an after market HU with the Monsoon amp & speakers. I just posted that info about the Circiut City installer for intertainment purposes.

But I am interested in any info on using the stock Onstar GPS antenna. Yeh, I figured it may be more of a pain to use the stock antenna then just installing a new one. My big concern is having another antenna somewhere visable on the car.

Bonneville Club :: View topic - In Dash Navigation Unit.

Even though it is a bonneville forum, you might find this thread really helpful. You should just be able to set the new antenna beside the stock one and it will never be seen.

__________________
Steven Oliver
2004 GTP comp-g WS6. Gator and suede all around interior.
Advanced MECP certified installer, custom upholsterer.