To find it definitively, you'll need to:
* Consult your owner's manual: The manual should have a diagram showing the location of all major components.
* Use a repair manual: A Haynes or Chilton repair manual for your specific year and model will provide detailed diagrams and descriptions.
* Look for a large, cylindrical pump with hoses connected: The AIR pump is usually fairly substantial and has several hoses leading to it. Follow these hoses to help you locate it.
* Use an online parts diagram: Websites selling Cadillac parts often have diagrams that show the location of components. Search for "2001 Cadillac DeVille parts diagram" and specify your engine type if you know it.
Be aware that the area around the pump can be hot when the engine is running, so exercise caution.