The spark plugs on a Cadillac Catera (which is essentially a rebadged Opel Omega B) are located on
the top of the engine, but accessing them can be a bit tricky. They're not easily visible without removing some components. You'll likely need to remove parts of the intake manifold or other components to reach them, depending on the specific engine (the Catera used different engines across its production run).
Because of this difficulty, consulting a repair manual specific to your Catera's year and engine is strongly recommended. A Haynes or Chilton manual will show you exactly where the plugs are and the steps involved in accessing and replacing them. Trying to find them without a proper guide could lead to damage or unnecessary work.
