On a 2004 Chevy Silverado 2500, the fuel filter is located
on the frame rail, near the fuel tank, on the passenger side of the vehicle. It's usually fairly close to the rear axle. However, the exact location can vary slightly depending on the specific engine and configuration of your truck. It's often mounted in a bracket and may be somewhat difficult to access.
It's recommended to consult your owner's manual or a repair manual specific to your truck's year, make, model, and engine for the most precise location. A visual inspection with the help of a diagram will be more certain than a generalized answer.
