Aftermarket Stereo Install? (First Time Grand Prix Owner/ First Time Forum User)

[Kickflip Supreme]

Hi Everyone.

I just bought my first Grand Prix (2004 GTP), and I'm curious about doing a stereo install. I've done stereo installs myself on previous vehicles that I've owned, but when I discovered everything that comes into play on an 04 GTP, I was actually overwhelemed. So here's the deal. I want to remove the stock CD player and replace it with a Pioneer SPH-DA120 (with Apple CarPlay and all that fancy crap). After doing my research, It is to my understanding that it fits in my vehicle. My main concern is, since my vehicle has both a Monsoon system, and OnStar, do I absolutely NEED to get a special wiring harness? I understand that if I get a normal harness, I will lose OnStar (Which I am more than completely fine with). But will I need to get a special harness just because of the sole fact that I have a Monsoon system? And If so, does that special harness need to be the one that retains OnStar and all of that? I was a bit confused when I saw the stock headunit has two ports in the back, whereas my new headunit only has one. Do I just let the black one hang there? I also have the PAC steering wheel control adapter to retain steering wheel functions (if that's even possible). Sorry about the lengthy post. This is my first time posting on a car forum.

[Kickflip Supreme]

I also can't figure out how to remove the hyperlinks over certain phrases.

[Peirce1970]

As long as your still using the Monsoon amp your gonna have to have a GMOS-01 harness to keep running the factory amp unless you go through a whole bunch of research on wiring and I still don't know that you could make it work. I've had mine both ways( with the monsoon amp and bypassing the amp) currently in the 04 that I have now I have replaced everything with aftermarket equipment.


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[Kickflip Supreme]

Ok. Awesome. Thank you for shining some light onto the situation. I just ordered the GMOS-01. It looks simple enough to install. I've just never had a vehicle where I had so many factors come into play haha. I was a bit overwhelmed.

[Peirce1970]

It's not that hard with the harness. I had mine hooked up for a while with a pioneer double din DVD player using the monsoon amp and speakers and running a sub box for lows. It sounded pretty good. You said that you are getting a Pioneer app radio right? If so do you know about the micro bypass to be able to watch video? Pioneer changed their head units in 2013 so it takes a dual pulse ground to be able to get video.


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[simbah]

As long as your still using the Monsoon amp your gonna have to have a GMOS-01 harness to keep running the factory amp unless you go through a whole bunch of research on wiring and I still don't know that you could make it work. I've had mine both ways( with the monsoon amp and bypassing the amp) currently in the 04 that I have now I have replaced everything with aftermarket equipment.


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Actually with the Monsoon system you would need the GMOS-04 harness not the 01. The 01 harness is for non Monsoon systems, Or if you wish to bypass the Monsoon amp and wire your speakers directly to the headunit.