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Solving the mystery of brake warning light for Fairfax, VA residents

July 15, 2020

Solving the mystery of brake warning light

Our team at ABS Unlimited regularly gets calls for concerned customers and non-customers alike about the fact their brake warning light has just come on. They generally want to know whether it’s a serious problem that requires immediate attention or if it’s something more precautionary that they can have inspected during their next routine visit to the shop. 
Each time, our ASE certified mechanics find ourselves recommending that brake warning light is something that should be evaluated quickly and not something that should be ignored. In our experience, we find the cause of the brake warning light to be one of the following: 

Parking Brake Set

an image showing parking brake light

In some vehicles, the brake warning light remains on while the parking/emergency brake is in the set position. This is meant to serve as a reminder to the driver that the parking brake needs to be disengaged before driving. 

In other vehicles, the parking brake light can be a separate light altogether or It could be represented by an Icon that has the letter P in the center circle. This type of indicator is usually found in vehicles with automatic or e-brakes. 

How to resolve this issue?

Disengaging your parking/e-brake should cause the brake warning light to go away. Parking brake locations can vary from vehicle to vehicle so if you are not sure on how to disengage your parking brake, Wagner provides a great resource titled All About Your Emergency Brake

However, if you are having a problem disengaging your parking brake because it’s stuck, then consider reading this article. – Troubleshoot a parking brake. 

Worn Brake Pads/Low Brake Fluid

This is the most common cause of brake warning light illumination. If the light comes on when the brake is applied and/or it stays illuminated continuously then it is likely for one of the following reasons: 

  1. Fluid level in the master cylinder is low – This occurs because worn brake pads cause brake caliper pistons to extend further in order to ensure the brake can be applied effectively. The extra space created inside the caliper is filled with brake fluid which causes the fluid level in the master cylinder to drop. 
  2. Hydraulic pressure in one side of the braking system has been lost
  3. Brake pads are worn – For vehicles equipped with electronic wear sensors, a brake warning light is triggered when the brake pads are beyond a minimal thickness. The following video by Powerstop offers a good explanation

How to resolve this issue?

In each of the above listed scenarios, the brake fluid level in the master cylinder and/or the thickness of the brake pad should be evaluated. If the fluid level is low, filling the master cylinder reservoir with additional brake fluid may be a good temporary solution. 
Here’s a good video by Advanced Auto Parts on how to check your brake fluid level.

Leaky Brake System

If your brake fluid is low, you should get your brakes checked by a professional immediately. An easy way to tell that is if your brake pedal is low or you have to pump your brakes repeatedly for the vehicle to stop. 

If you experience this condition, please pull over immediately and have your vehicle towed to your preferred service facility or ABS Unlimited in Fairfax, VA for repairs. 
The low brake fluid level can be a result of a leak any of the following areas:

  • Brake lines
  • Brake hoses
  • Wheel cylinder (drum brakes)
  • Brake calipers (disc brakes)
  • Master cylinder

Leaking brake fluid can cause brakes to slip or grab due to contamination. You may notice this to be a problem if your vehicle pulls to one side when braking. 

How to resolve this issue?

Bring your vehicle to your mechanic immediately.

ABS Warning Light Ignition

Vehicles equipped with anti-lock braking system (ABS) come with a specific warning light that is intended to warn drivers of an issue with the ABS system. This light is lit when the vehicle is initially turned on, but it’s then intended to turn off once the vehicle’s system determines that everything is in working order. However, if the light doesn’t turn off or comes on while driving, it’s meant to warn the driver of an issue with the ABS system. If this happens, the ABS system is disabled automatically until the problem is resolved.  

The good news is that in the case where this light is illuminated, the normal braking system of the vehicle continues to operate.  However, it is important to note that while the ABS light is illuminated, the ABS system WILL NOT be available in case of an emergency or while driving on a wet surface.

A faulty vehicle speed sensor (VSS) is a common issue that can cause the ABS light to come on. A vehicle speed sensor is a type of tachometer that is used to read the speed of a vehicle’s wheel rotation and provide update to the ABS system in order to aid in maintaining control of the vehicle. 

How to resolve this issue?

An illuminated ABS light indicates a significant problem with your ABS system. It is strongly recommended that you bring your vehicle to a mechanic immediately for evaluation.