See GM Bulletin 03-08-57-001 A. It says the horizontal seam on the left rear fender well is not properly sealed or has a hole. Water travels along the sill plate to the front driver carpet as well. It can be repaired with sealer.
I removed my carpet and had my son watch where the water was coming in. Sure enough, it was the left rear fender well. Good luck.
Friday, January 23rd, 2015 AT 8:10 AM