* Brake System Issues: These are the most common causes.
* Low brake fluid: This is the most frequent culprit. Check the brake fluid reservoir (usually a clear plastic container near the master cylinder) and add fluid if it's low. However, adding fluid without addressing the underlying cause is only a temporary fix and potentially dangerous. Low fluid usually indicates a leak somewhere in the system.
* Brake wear: Worn brake pads or shoes trigger the warning light. The sensors in the brake system detect pad thickness. This requires replacement.
* Brake system leak: A leak in the brake lines, wheel cylinders, calipers, or master cylinder will cause a fluid loss and trigger the warning light. This needs immediate professional attention.
* Faulty brake light switch: This switch activates the brake lights when the brake pedal is pressed. A faulty switch may illuminate the warning light even when the brakes aren't applied or fail to illuminate the brake lights at all.
* Faulty ABS sensor or module: The Anti-lock Braking System (ABS) is closely tied to the brake system. A problem with an ABS sensor or the ABS module itself can also trigger the brake light. This usually requires diagnostic equipment to pinpoint the problem.
* Faulty Parking Brake (Emergency Brake): Sometimes, a partially engaged or malfunctioning parking brake can trigger the light. Make sure the parking brake is fully released.
* Electrical Issues: Less common, but still possible:
* Faulty brake light bulb(s): While the burned-out brake lights might not always trigger the dash light, sometimes it can, particularly if the system is poorly wired or the bulb failure is sensed as a short circuit. Check your tail lights and the center high-mounted stop light (CHMSL).
* Wiring problems: Damaged or corroded wiring in the brake light circuit can cause the light to come on.
* Faulty dashboard indicator bulb: Although rare, the bulb in the instrument cluster responsible for the brake light warning could itself be burned out and thus always illuminated. This is easily ruled out by checking the other warning lights.
What to do:
1. Check the brake fluid level. This is the first and easiest thing to do. Low fluid necessitates investigation into the cause of the fluid loss.
2. Inspect brake lights: Check all brake lights (tail lights and CHMSL) to ensure they're working.
3. Check the parking brake: Ensure it's fully released.
4. Consult a mechanic: If the issue persists after these initial checks, it's crucial to have a professional mechanic diagnose the problem. They have the tools and expertise to pinpoint the exact cause and perform the necessary repairs safely. Ignoring a brake light warning is extremely risky.
Ignoring a brake light warning can lead to brake failure, which is extremely dangerous. Have it checked immediately.
