* Burnt-out bulbs: This is the most common cause.
* Blown fuse: Check the fuse box for a blown fuse related to the brake lights.
* Faulty brake light switch: This switch is activated when you press the brake pedal. A malfunctioning switch prevents the circuit from completing.
* Wiring issues: Corrosion, broken wires, or loose connections anywhere in the brake light circuit can prevent them from working.
* Bad ground: A poor ground connection can interrupt the circuit.
* Taillight issues: Problems within the taillights themselves (besides the bulbs) could be at fault.
To troubleshoot, you'll need to systematically check these possibilities. A wiring diagram for your specific year and model truck would be helpful. You can find these online or in a repair manual.
