Side Door Lock Cylinder Coding
WARNING: This page is about a different car, the 2005 GMC Canyon and 2005 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.
The side door lock cylinder has five snap-in tumblers. The number 1-5 positions (beginning closest to the cylinder head) is a brass retainer tumbler. The 6-10 positions are standard tumbler positions. Therefore, only the 6-10 positions are required.