The EGR valve on a 2002 Cadillac DTS (with the Northstar engine) is located on the
passenger side of the engine,
near the back, relatively close to the firewall. It's often somewhat tucked away and might require some maneuvering to see clearly. You'll likely need to remove some components (like heat shields) for easier access.
Because of its location and the potential for obstructions, a picture or diagram specific to the 2002 Cadillac DTS engine is highly recommended before attempting to locate it yourself. A repair manual or online resources showing the engine bay layout will be invaluable.
