* Low Brake Fluid: This is the most common and often the simplest cause. Check your brake fluid reservoir (usually a clear or translucent container) located under the hood. If the fluid level is low, you have a leak somewhere in your brake system – a serious issue requiring immediate attention. Do not drive the car until this is addressed.
* Brake System Leak: A low fluid level is a *symptom* of a leak. The leak could be anywhere in the brake lines, wheel cylinders, calipers, or even the master cylinder. A mechanic needs to locate and repair the leak.
* Faulty Brake Light Switch: This switch signals the brake lights to illuminate when the brake pedal is pressed. If it's faulty, it might be sending a constant signal, even when the pedal isn't depressed, thus turning on the brake lights. It could also be related to the ABS light staying on as a result of a fault sensed within the brake system.
* Faulty ABS Module or Sensor: While less likely to cause both lights simultaneously *initially*, a failing ABS module or a faulty wheel speed sensor could eventually trigger both lights. The ABS system relies on proper brake pressure and wheel speed readings, so a problem in either could eventually lead to the brake light coming on as well. Diagnosing this requires a more advanced scan tool.
* Worn Brake Pads/Shoes: Severely worn brake pads or shoes can sometimes trigger the ABS light indirectly if it affects the wheel speed sensors' readings or creates enough drag to influence the system.
What to do:
1. Check the brake fluid level immediately. This is the most important first step.
2. Do not drive the car if the fluid is low. Driving with low brake fluid is extremely dangerous.
3. Have a qualified mechanic inspect the braking system thoroughly. They will have the tools to diagnose the issue accurately and perform the necessary repairs. Ignoring this could lead to brake failure.
The ABS and brake light combination is a serious warning sign. Don't delay getting your car inspected.
