1. The Simple Checks (Easiest First):
* Bulbs: This is the most common cause. Check both brake light bulbs (one on each side) for breakage or burn-out. It's possible *both* failed simultaneously, though unlikely. Replace them with new bulbs of the correct wattage.
* Fuses: Locate the fuse box (usually under the hood or inside the cab) and check the fuse(s) related to the brake lights. The owner's manual will show you the fuse layout and which fuse(s) are responsible. A blown fuse will be visibly broken (a thin wire inside will be severed). Replace any blown fuses with fuses of the correct amperage.
* Brake Light Switch: This switch is usually located near the brake pedal. It's activated when you press the brake pedal, completing the circuit to illuminate the lights. Visually inspect it for damage or loose connections. You can test it with a multimeter (more on this below).
2. More Involved Troubleshooting (Requires Tools):
* Wiring: Inspect the wiring harness from the brake light switch to the tail lights. Look for broken wires, corrosion, or loose connections. A visual inspection is often enough to spot obvious problems. If you see any damage, you may need to repair or replace the wiring.
* Brake Light Switch Testing: Use a multimeter (set to continuity test) to check the brake light switch. With the ignition ON, one multimeter lead should touch the switch's connector, the other lead to ground. When you press the brake pedal, the multimeter should show continuity (a closed circuit). If not, the switch is bad and needs replacing.
* Tail Light Wiring/Connectors: Check the wiring and connectors at the tail lights themselves. Corrosion or loose connections are common culprits.
* Ground Connection: A poor ground connection can prevent the brake lights from working. Trace the ground wire from the tail lights and ensure it's securely connected to a good ground point (usually bare metal on the vehicle's chassis).
3. Less Likely, But Possible:
* Brake Pedal Position Sensor (if equipped): Some vehicles use a sensor to monitor brake pedal position. A faulty sensor could prevent the brake lights from activating. This is less likely on an older truck like yours.
* Central Control Module (CCM) or BCM (Body Control Module): While less common in older vehicles, a faulty BCM could interfere with brake light operation. Diagnosing this usually requires a scan tool to check for error codes.
Important Note: If you're not comfortable working with car electrical systems, it's best to take your truck to a qualified mechanic. Incorrectly diagnosing and repairing electrical issues can be dangerous. A multimeter is an invaluable tool for electrical diagnostics, though. If you decide to tackle this yourself, be careful and make sure to disconnect the negative battery cable before you start.
