WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: View Of Piston Oil Cooling Nozzle Inspection Areas
Courtesy of GENERAL MOTORS CORP.
Inspect the piston oil cooling nozzle for damage.
Replace the piston oil cooling nozzle if any damage is found.