GM engineers design the sliding glass panel in order to control water entry at the seal. Adjust the glass panel properly in order to ensure a tight fit between the weatherstrip and the roof. Use the following procedure in order to verify a proper fit between the weatherstrip and the roof:

1. Open the roof.
2. Insert a piece of paper between the weatherstrip and the roof.
3. Close the roof.
4. Pull the paper out.

Verify that there is some resistance on the paper when you pull the paper out. A small gap prevents water and debris from overloading the sunroof drain hoses. A small gap also prevents objectionable wind noise. Adjust the sunroof window by adjusting the height and centering of the glass. Refer to Sunroof Window Height and Opening Fit Adjustment .

A drain trough in the sunroof module drains the sunroof. The drain trough encircles the sliding glass panel. A drain channel spans the rear of the sunroof module. The drain channel directs water into the drain trough.

The drain trough leads to drain hoses located in each corner of the housing. The drain hoses route down the windshield pillars. The drain hoses discharge at the center of each pillar between the upper and lower door hinges. The rear drain hoses route down the rear pillars into the rear wheelhouse.

If the headliner is wet or water leaks occur, verify that the drainage system is not plugged or disconnected using the following procedure:

1. Use a small container in order to pour water into the module housing drain trough.

Important: When using compressed air on the drain hoses, care should be taken not to use it in excess.

2. If the drain system is clogged, use compressed air or a flexible wire in order to clear out any material that is plugging the drain system.
3. Test the drain system again.

Use the following procedure in order to inspect the drain hose connections without completely removing the headliner:

1. Remove the sunroof control switch.
2. Remove the sunroof opening trim lace from around the sunroof opening.
3. Lower the headliner as necessary in order to inspect the drain hose connections.