Open driver's door. Look between door an fender and bottom of door. In the post area there is a covering over the wheel well that lets dirt and water into area. I just happened to be cleaning car and noticed debris in this area. When I went to brush it out noticed that it was packed into post. On the driver's side I got over 3 cups of dirt and other debris out. Obviously creating rusting problem. Insulation was wet. Both sides were like this. Took a straightened hanger to clean out. Obviously another design flaw that hastens rusting of car. Also bottoms of drivers and passengers doors rusting.. If I had known these weaknesses when car new i would have paid attention to these areas and pointed out to dealership and worked to prevent rusting.. Seems that some of these design flaws are purposeful so that car will rust and will need to buy new one! I do think GM should fix these common design flaws free of charge!