I'm not at work right now, so I don't have the procedure book with me. I checked on line and there is one available for your vehicle.
I can tell you this, most GM vehicles have them located near the cowl. Open the hood. On the passenger side, between the windshield and firewall, there is a black plastic cover. Check for plastic push pins that hold it in place. Remove the pins and lift the plastic cover. Look down inside. This is where the air enters the HVAC system. There should be a filter there which is to clean the air entering the cabin much like a furnace filter in your home does.
If the filter is extremely dirty, it WILL cut down on the air supply to the fan causing low air flow in the vehicle. I don't know what made this pop into my head, but I feel it is something that should be checked.
Let me know what you find. I will be online for about another 15 minutes. If you can, let me know what you find. If I am incorrect, I can check location tomorrow for you.
Let me know.
Tuesday, July 29th, 2014 AT 8:30 PM