To find it, you'll likely need to:
1. Consult your owner's manual: This is the best resource, as it will show you a diagram of your fuse box and relay locations.
2. Look for a fuse box or relay panel: Under the dashboard on the driver's side is the most common place. You might need to remove a panel or cover to access it.
3. Identify the flasher relay: It might be labeled, or you can use the owner's manual diagram to find the correct relay. It's usually a small square or rectangular component with several connectors.
If you can't find it using these steps, searching online for "2004 Chevrolet Impala fuse box diagram" with images might help you visualize the location. Remember to disconnect the negative battery terminal before working with electrical components.