* Brake Light Switch: This is the most frequent cause. The brake light switch is a small switch located near the brake pedal. It's designed to close the circuit and activate the brake lights when the pedal is pressed. If it's malfunctioning, it might be stuck in the "on" position, even when the pedal is released. This is a relatively inexpensive and easy part to replace.
* Wiring Issues: Worn, frayed, or shorted wires in the brake light circuit can cause the lights to remain illuminated. This could be anywhere from the switch to the lights themselves. Look for damaged wiring near the brake pedal, under the dash, and along the frame rails. Corrosion at connections is also a possibility.
* Brake Pedal Position Sensor (if equipped): Some vehicles use a sensor to monitor brake pedal position, and a faulty sensor could send an incorrect signal, keeping the lights on.
* Faulty Brake Light Bulbs (less likely): While less likely to cause *all* brake lights to stay on, a shorted bulb could potentially cause a short circuit affecting the entire system. Check the bulbs themselves; a shorted filament might be causing this.
* Central Control Module (rare): In rare cases, a problem with the vehicle's central control module or a related computer could be responsible. This is a less likely cause unless other electrical issues are present.
* Grounding Problem: A poor ground connection in the brake light circuit can cause current to flow improperly, leading to the lights staying on.
Troubleshooting Steps:
1. Visually Inspect the Brake Light Switch: Look for any obvious damage or signs of wear.
2. Check the Brake Light Bulbs: Make sure none are burnt out or shorted.
3. Inspect the Wiring: Look for any frayed, broken, or corroded wires in the brake light circuit. Pay close attention to the areas near the brake pedal and the tail lights.
4. Test the Brake Light Switch (if comfortable): There are ways to test the switch with a multimeter (a simple electrical tester). You can find videos online demonstrating how to do this.
Important Note: Driving with your brake lights constantly on is unsafe. It can lead to other drivers assuming you're braking and potentially causing an accident. It's crucial to address this issue promptly. If you're not comfortable performing these checks yourself, take your Expedition to a qualified mechanic for diagnosis and repair.
