* Brake Light Switch: This is a very common cause. The switch is located near the brake pedal and activates when you press the pedal. It's a relatively inexpensive part and easy to replace (though access might be a little tight depending on the Lumina model). Test the switch with a multimeter to confirm it's making contact when the brake pedal is depressed. A simple continuity test will determine if it's working.
* Wiring: Check the wiring harness running from the brake light switch to the tail lights. Look for broken wires, corrosion, or loose connections. Pay close attention to the areas where the wiring might flex or bend frequently.
* Brake Pedal Position Sensor: Some vehicles use a separate sensor to signal the brake pedal position. This is less common on older vehicles, but it's possible. A diagnostic scan tool can be used to check for trouble codes related to this.
* Central Brake Junction Block/Tail Light Junction Block: There's a junction block or module that acts as a central point for the brake light circuit. A faulty junction block or its connections could interrupt the current.
* Body Control Module (BCM): In some cases, the BCM controls the brake lights. A malfunctioning BCM could prevent the lights from activating. This is less likely, but a diagnostic scan is needed to check.
* Grounding Issues: A poor ground connection could prevent the brake lights from working properly. Inspect the ground wires near the taillights and the brake light switch for corrosion or looseness.
Troubleshooting Steps:
1. Test the brake light switch: Use a multimeter to check for continuity when the brake pedal is depressed.
2. Visually inspect the wiring: Carefully examine the wiring harness from the switch to the tail lights for any damage.
3. Check the tail light sockets: Ensure the sockets themselves aren't damaged or corroded.
4. Use a test light: A test light can help trace the circuit, showing you where the power is lost. You can probe the wires at different points in the circuit to pinpoint the break.
5. Obtain a Wiring Diagram: A wiring diagram for your specific year and model Lumina will be extremely helpful in tracing the circuit and locating the various components. You can find these online, often through repair manuals or forums dedicated to the Chevrolet Lumina.
6. Diagnostic Scan Tool: If all else fails, using a OBD-II scan tool could reveal diagnostic trouble codes (DTCs) pointing to the problem.
Remember safety first! Disconnect the negative battery terminal before working with the electrical system. If you're not comfortable working with automotive electrical systems, it's best to take your Lumina to a qualified mechanic.
