* Brake Light Switch: This is the most common cause. Located near the brake pedal, it's a simple switch that closes when you press the brake pedal, completing the circuit to the brake lights. It can wear out, get misaligned, or become damaged. Testing it with a multimeter is relatively straightforward.
* Wiring: A break or short in the wiring between the brake light switch, the fuse box, and the lights themselves can interrupt the circuit. This could be anywhere along the wiring harness, including within the vehicle's body. Visual inspection for damage is needed, and a multimeter can help pinpoint a break.
* Brake Pedal Position Sensor (Sometimes integrated with the switch): Some vehicles have a sensor that tells the computer the position of the brake pedal. A faulty sensor might prevent the computer from sending the signal to illuminate the brake lights. This is less common than a faulty brake light switch but possible.
* Body Control Module (BCM): This computer controls various functions, including the brake lights. A faulty BCM could prevent the lights from working even if all other components are fine. Diagnosing a BCM issue usually requires specialized tools and knowledge.
* Grounding Issues: A poor ground connection somewhere in the brake light circuit can prevent the lights from working. This requires checking the ground wires for corrosion or loose connections.
* Trailer Wiring (If applicable): If you frequently tow, a short or problem in the trailer wiring harness could draw power away from the vehicle's brake lights, or even short them out completely.
Troubleshooting Steps:
1. Visual Inspection: Carefully examine all wiring related to the brake lights, looking for any obvious damage, corrosion, or loose connections. Pay particular attention to the area around the brake pedal and the wiring harness running to the taillights.
2. Test the Brake Light Switch: This is the easiest thing to check first. You'll need a multimeter to test continuity when the brake pedal is pressed. There are many online tutorials showing how to do this.
3. Check for Power at the Bulbs: Use a test light or multimeter to check if power is reaching the brake light sockets when the brake pedal is depressed. If no power is present, the problem lies upstream (closer to the switch).
4. Check the Ground: Ensure a good ground connection at the taillight assembly.
If you're not comfortable working with car electronics, it's best to take your Suburban to a qualified mechanic for diagnosis and repair. They have the tools and expertise to quickly identify the problem.
