The power steering fluid reservoir on a 2004 Pontiac Sunfire is typically located
under the hood, near the power steering pump. It's usually a small, clear or translucent reservoir with markings indicating the minimum and maximum fill lines. Look for a cap that might say "Power Steering Fluid" or have a steering wheel symbol.
Because there's variation in the exact location depending on engine and trim level, I strongly recommend consulting your owner's manual. It will have a diagram showing the precise location of the reservoir and instructions on how to properly check and add fluid.
