Where are the spark plugs on a 2002 Chevy Trailblazer?

The spark plugs on a 2002 Chevy Trailblazer are located on top of the engine, under the plastic engine cover. To access them, you'll need to remove the engine cover. They're arranged in a V-pattern following the cylinder head layout of the engine. There will be one plug per cylinder. The exact location relative to the front and sides of the vehicle will vary slightly depending on whether you have the 4.2L inline 6-cylinder or the 5.3L V8 engine. A repair manual or online diagrams specific to your engine type will show the precise location of each plug.