Where is the emissions pump on a 2004 Chevy Trailblazer?

The 2004 Chevy Trailblazer, depending on the engine, may not have an emissions pump. Many vehicles of that era transitioned away from the older style Air Injection Reaction (AIR) systems that used these pumps.

If your Trailblazer *does* have one, it's typically located near the exhaust manifold and will be a small, electrically driven pump. However, it's best to consult your owner's manual or a repair manual specific to your Trailblazer's engine (e.g., 4.2L I6, 5.3L V8) to be certain of its location and even its existence. Looking at diagrams specific to your engine will be more helpful than general information.