Diagnostic Aids
WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
If the vehicle is equipped with the 2.8L and 3.6L engine, the transmission is in neutral with the engine operating, and a whirling kind of a noise, neutral gear rattle, is heard outside the vehicle, this is a normal condition.