Circuit/System Testing
WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
Inspect for an incorrectly installed timing chain, excessive play in the timing chain, or for a timing chain that jumped teeth. Refer to Camshaft Timing Drive Chain Alignment Diagram and Camshaft Timing Drive Components Cleaning and Inspection .