To find it, you need to consult your owner's manual. This is the most reliable source. It will show you the location of the fuse box(es) (under the hood and possibly inside the cabin) and a diagram to identify the correct fuse or relay.
If you don't have the owner's manual, you can try:
* Online Resources: Search for "2004 GMC Envoy fuse box diagram" on Google Images. This will yield several diagrams. However, be cautious as diagrams vary slightly depending on trim level and options. Double-check that the diagram matches your vehicle.
* GMC Website: The official GMC website might have downloadable owner's manuals.
* Auto Parts Store: Auto parts stores like AutoZone, Advance Auto Parts, or NAPA can often access online diagrams or have printed ones in-store.
Remember, working with automotive electrical systems can be dangerous. If you're not comfortable with this task, take your Envoy to a qualified mechanic.