1. Check the Fuse: Your owner's manual will show you the fuse box location and diagram. Locate the fuse specifically for the CHMSL. Check if it's blown. If so, replace it with one of the same amperage. However, if the fuse blows immediately after replacement, there's a short circuit somewhere in the wiring.
2. Inspect the Bulb: Access the CHMSL bulb (usually located in the rear spoiler or above the rear window). Check if the bulb is burnt out. Replace it if necessary. Make sure it's the correct type of bulb.
3. Examine the Wiring and Connections: This is the most challenging step. Carefully inspect the wiring harness leading to the CHMSL for any signs of damage, chafing, corrosion, or loose connections. Pay close attention to the connections at both the light and the vehicle's electrical system. A multimeter can help check for continuity and voltage at the connections.
4. Check the Brake Light Switch: While less likely if the outer brake lights are working, a faulty brake light switch could still affect the CHMSL, especially if the switch is sending a weak signal.
5. Ground Connection: A poor ground connection for the CHMSL could prevent it from lighting up. Check the ground wire for corrosion or loose connections.
6. Body Control Module (BCM): In some cases, the BCM could be faulty and not sending the correct signal to the CHMSL. This is less common but possible. Diagnosing this requires more advanced tools and knowledge.
Important Safety Note: Always disconnect the negative battery terminal before working on any electrical components in your vehicle.
If you're not comfortable working with car electrical systems, it's best to take your Lumina to a qualified mechanic for diagnosis and repair. Ignoring a malfunctioning brake light is a safety hazard.
