1. Identify the Problem:
* Is only one side out? This points to a localized issue (bulb, socket, or wiring on that side).
* Are both sides out? This suggests a more central problem (fuse, BCM, or main wiring harness).
* Are the brake lights working? If the brake lights work but not the running lights, the problem is likely in the running light circuit itself.
* Is there any flickering or dimming? This could indicate a loose connection or a failing component.
2. Simple Checks:
* Check the fuses: Consult your owner's manual to locate the fuse box and identify the fuse(s) for the rear running lights. Replace any blown fuses.
* Check the bulbs: Access the taillight assemblies (usually requires removing screws or panels). Inspect the bulbs for burnouts or damage. Replace any faulty bulbs with the correct type (refer to your owner's manual). This is often the simplest solution.
* Inspect the bulb sockets: While you have the bulbs out, carefully examine the sockets for corrosion, loose connections, or broken contacts. Clean any corrosion with a wire brush or contact cleaner and ensure good contact.
3. More Involved Troubleshooting:
* Wiring Inspection: If the bulbs and sockets are fine, you'll need to trace the wiring. This requires a multimeter to test for continuity and voltage. Start at the bulb socket and work your way back towards the fuse box, checking for breaks in the wiring or poor connections at connectors. This is difficult and requires some electrical knowledge and patience. A wiring diagram specific to your Reatta's year is crucial here.
* Body Control Module (BCM): The BCM controls many electrical functions in the Reatta, including lighting. If you've ruled out everything else, a faulty BCM could be the culprit. This is a more advanced repair and usually requires professional diagnosis and replacement.
4. Accessing the Taillight Assemblies:
The exact procedure for accessing the taillights varies slightly depending on the year of your Reatta. Generally, it involves:
* Inner Trunk Access: You'll likely need to access the taillights from inside the trunk.
* Interior Trim Removal: This typically involves removing interior trim panels in the trunk area to reach the taillight assemblies. Be careful to avoid breaking any plastic clips.
* Screw Removal: The taillight assemblies are usually held in place by screws. Remove these screws to access the bulbs and sockets.
Important Considerations:
* Wiring Diagram: Obtain a wiring diagram specific to your Buick Reatta's year. This is essential for tracing wires and identifying the correct circuits. You can often find these diagrams online (e.g., online forums dedicated to Buick Reattas) or through a repair manual.
* Safety: Disconnect the battery's negative terminal before working on any electrical components to avoid short circuits or shocks.
* Professional Help: If you're not comfortable working with car electrical systems, it's best to consult a qualified mechanic. Improper repairs can lead to further damage or safety hazards.
Remember to always refer to your owner's manual for specific instructions and diagrams related to your Reatta's year and model. Good luck!
