AXXESS GMOS-04 Data Interface Module - Compatible with 2000-2013 Select GM Vehicles | Plug & Play Car Stereo Installation | Perfect for Aftermarket Radio Upgrades in Chevy, GMC, Buick & Cadillac

I didn't even know my 2006 Pontiac Grand Prix had a factory amplified sound system until I went to best buy to get a wire harness to install an after market head unit and they told me the harness was going to be over $200. They explained to me what kind of system these Grand Prix come with stock. Well, I am hard headed and I have never had to pay over $20 for a wire harness so I still bought the $17 harness and thought maybe I could just figure it out on my own with out having to pay more for the harness than I did for head unit. I installed the cheap harness and got everything up and running but everything sounded like junk and factory radio ended up sounding MUCH better than my after market. My speakers were hissing to the point it was embarrassing me if anyone got into my car. So then i bought an OEM output converter and that actually did help with the hissing but then i still couldnt make any equalizing adjustments from the head unit. I am sound stereo hobbiest so i have all sorts of different equipment in my garage and i am constantly switching out different amplifiers and subwoofers, etc. and even though the OEM took care of the hissing, I still could not do anything else adjustment wise because the factory amplifier is already set at the exact settings for factory speakers and the factory radio doesn't have equalizing adjustments like the aftermarket radio does. So, to shorten this up your factory speakers are already getting equalized by the factory amp, you can not send your your speakers a SECOND sound wave of the same kind of settings. So you do need a harness like this one. If you are looking for just getting rid of the hissing then Google OEM's but if you are like me and like to have control of your own settings then you NEED this wire harness. Trust me, I spent 2 months of trying anything I could possibly do to NOT buy the more expensive harness. I got this harness and now I can bump my subwoofers and adjust my factory speaker. I personally still kept my cheap harness because I plan on ripping every single factory audio wire out of this car and building my own, but this harness works for me until then. Good luck and save the struggle. Buy this harness. If you have not read by now then just know this harness does NOT come WITH the steering wheel functions but this harness does come compatible for you to use a harness for steering wheel functions and that is important to know because not all harnesses are compatible for the AW1 AND you will be stuck with a $60 steering wheel harness and still no way of being able to use it. This harness has a pigtail for the AW1 so do your self a favor and forget about how much it is going to cost for this harness and the steering wheel controls. I personally wish I could have found a way to pick and choose out of the 4..... 1. Door chimes, 2. Aftermarket head unit, 3. Onstar (really? Who still uses onstar but atlease the wiring is already ran to the mirror for when I install a dash cam) and 4. Steering wheel functions) all I wanted was my steering wheel and head unit but this harness made me happy for now and I'll just sell it on Ebay later. Good luck with your system and for what it is you are doing to your car that has a factory amp you need this harness. Thanks