1. Faulty wiring: Inspect the wiring harness that connects the tail lights and license plate to the vehicle's electrical system. Look for any frayed, damaged, or corroded wires, and repair/replace as needed.
2. Faulty relay: The tail lights, license plate, and turn signals may share a common relay. If this relay fails, it can affect the operation of these lights. Check the relay and replace it if necessary.
3. Bad ground connection: A poor ground connection can cause electrical issues such as this. Check the vehicle's ground points, particularly those in the rear, for any corrosion or loose connections. Clean or tighten the ground connections as necessary.
4. Faulty switch: The turn signal switch or the brake light switch may be malfunctioning, affecting the operation of these lights. Inspect and test these switches to ensure they are functioning properly.
5. Electrical module issue: Some modern vehicles have electronic modules that control the lighting system. A fault in one of these modules could lead to the failure of the tail lights, license plate light, and turn signals. Have the vehicle's computer system diagnosed by a qualified technician.
6. Faulty fuse: While you have already replaced fuses, verify that the right ones were used and they are making proper contact in their respective slots.
7. Faulty bulb sockets: If the bulb sockets are damaged or corroded, they may not make proper contact with the bulbs. Check the bulb sockets and replace them if necessary.
