Why is my brake system warning light on?

The brake warning light signals a problem with your braking system that needs attention. It can be something simple, like the parking brake being left on, or something more serious, such as a brake fluid leak or worn components. Do not ignore it and address it promptly.

Common triggers include an engaged parking brake, low brake fluid or leaks in the hydraulic system, worn brake pads or calipers, sensor faults, or ABS/control module issues. Note that ABS lights are separate and usually amber, while the red brake warning light indicates hydraulic or critical brake problems.

What this warning typically signals

The red brake warning light is usually a safety alert, indicating that the primary braking system may not be functioning properly. It can also appear if the parking brake is still engaged or if the hydraulic pressure in the brake system is compromised. Because braking performance is essential for safety, treat the warning seriously and consult a technician as soon as possible.

Common causes

Below are the most frequent reasons this light comes on, ranging from quick checks you can do yourself to issues that require a professional inspection.

• Parking brake is engaged or not fully released.


• Low brake fluid level or a leak in the brake hydraulic system.


• Worn brake pads or calipers, which can affect braking efficiency.


• Faulty brake fluid level sensor or other brake system sensors.


• Problems with the anti-lock braking system (ABS) or the hydraulic control unit.


• An electrical fault, such as a blown fuse or damaged wiring.


• Damage or leaks in brake lines or master cylinder failure.

These possibilities cover the majority of scenarios. The exact cause depends on the vehicle make, model, and age, so a professional diagnosis is often necessary to pinpoint the issue.

What to do if the light is on

Use this practical checklist to assess safety and outline next steps before driving again. Each item helps you determine whether you can continue to operate the vehicle or if you should seek immediate help.

1. Safely pull over and park in a safe location as soon as you can. If you’re in traffic or on a highway, use hazard lights and reduce speed gradually.


2. Check the parking brake. Ensure it is fully released. If the light stays on after you release it, the issue may be more than just the parked brake.


3. Check the brake fluid level in the master cylinder reservoir. If the level is low, inspect for leaks and top up with the correct type of brake fluid as specified by your vehicle’s manual. If you must top up, have the system inspected promptly to prevent further damage.


4. Look for visible signs of a leak under the vehicle or around the wheels. Any puddle or wet area is a red flag that requires professional service.


5. Assess brake pedal feel. If the pedal sinks, goes to the floor, or feels spongy, the system may have air or a pressure problem, requiring immediate diagnosis.


6. Limit driving and avoid hard braking. If you must move the vehicle, do so slowly and with light, gradual braking to minimize risk.


7. Book a diagnostic check with a qualified mechanic or dealership. They can read error codes, inspect fluid and pads, check for leaks, and test the hydraulic and ABS systems.

If the light persists after basic checks or you notice reduced braking performance, seek professional service without delay. Driving with a brake system warning light on can increase the risk of a crash if braking becomes unreliable.

Summary

The brake warning light is a critical safety signal that can indicate anything from a simply released parking brake to a serious hydraulic leak or sensor fault. Start with safe parking, verify the parking brake and fluid levels, check for leaks, and avoid aggressive braking. If the light remains or you notice any change in braking feel, have the vehicle inspected by a professional as soon as possible.

What two reasons would cause your brake system warning light to come on?

If your brake service warning light is on, it could indicate hydraulic issues, worn brake pads, or a need for parking brake adjustment. Because the brake service warning light could mean different things, it is best to have a brake specialist diagnose the issue.

Can I drive with a brake system warning light?

Drivers sometimes ask whether it's safe to drive with this brake light on. The answer is no; it should never be ignored. Brake system warning lights show that there is immediate risk and potentially a problem that compromises driver and vehicle safety.

How to fix brake system warning light?

To fix a brake system warning light, first check the simple things: make sure the parking brake is fully released and top off the brake fluid if it's low. If the light remains on, pull over safely and inspect for leaks or look for a professional diagnosis using an OBD-II scanner to read the trouble codes. 
Initial checks 
This video explains how to check the brake fluid level and look for leaks: 1mDashboard warning lights YouTube · Feb 29, 2024

• Check the parking brake: Ensure the parking brake is fully disengaged. Sometimes a separate indicator for the parking brake shares the same warning light. 
• Check brake fluid: Locate the brake fluid reservoir and check the level. If it's low, add the correct type of brake fluid specified in your owner's manual up to the "max" line. Low fluid can be caused by worn-out brake pads, so you may need to replace them as well. 
• Look for leaks: Check under your car for any puddles of fluid. If you see a leak, do not drive the car and call for a tow truck. 
• Check brake lights: Have someone check if your brake lights are working. A burnt-out bulb or a faulty brake light switch can trigger the warning light. 

Next steps for persistent warnings
This video demonstrates how to check for worn brake pads and the brake pad wear sensor: 57sPS AutomotiveYouTube · May 12, 2021

• Inspect brake pads: Look through the spokes of your wheels to see if the brake pads look thin. The warning light can indicate that the pads are worn and need to be replaced. 
• Use an OBD-II scanner: For a more precise diagnosis, use an OBD-II scanner to retrieve specific trouble codes from the car's computer. This can help identify issues with the Anti-lock Braking System (ABS) or other components. 
• Check wheel speed sensors: If a code points to the ABS, check the wheel speed sensors and their wiring for damage or dirt. 

When to seek professional help

• If you are unsure: If you have performed the initial checks and the light is still on, or if you find a leak, do not drive the vehicle further. 
• Arrange a tow: Have the car towed to a professional mechanic for a thorough inspection and repair. 
• Be safe: Driving with a faulty brake system can be extremely dangerous. A professional can safely diagnose and fix any issues to ensure your car is safe to drive. 

Is it expensive to fix a brake system issue?

A complete brake repair that includes pads, rotors, and calipers typically averages between $200 and $800 depending on the vehicle and parts used.