When that exclamation mark in a round circle comes up on the dashboard, the first thing you’ll ask yourself is „why is my brake light on“?
This warning light is one of the most important ones as it warns about possible problems with the brake system.
In this article, we’ll show you some most common reasons for why this happens and perhaps show you a way to find the solution.
1. PARKING BRAKE IS ENGAGED
This is the first and most obvious reason to check. Because of this, the brake light warning was invented in the first place.
Seems unlikely that you won’t notice it because of the resistance of the parking brake, but it does happen.
So, before any other inspection, see that the parking brake is fully disengaged.
In case of a mechanical parking brake, make sure the brake lever is completely down.
If you have an electronic one, make sure you’ve pressed the release button although this should happen automatically once the car has started to move.
2. LOW BRAKE FLUID LEVEL
A second and equally important reason for the brake warning light.
When you see that the parking brake is disengaged and the warning light is still on, immediately check the brake fluid level.
The whole procedure of how to do that is explained in another one of our articles which you can read by clicking here.
A common symptom of this problem is that the brake light will first light up occasionally and as the fluid level goes down, it will appear more frequently.
In the end, the light will be on all the time. A frequent low level of brake fluid certainly means you have problems with the brakes and should tend to it as soon as possible.
For more information about the most common brake problems, click here.
3. WORN OUT BRAKE PADS
Most of today’s cars have a very good warning system when the brake pads get worn out.
The usual system is that the brake pads have a built-in sensor. When the tip of the sensor reaches the brake disc, it lights up the brake warning light.
Since this happens when the brake pads are almost completely worn out, you should replace them as soon as possible.
In most cases, if you follow the maintenace schedules for your car, you’ll never get to the point where the brake light comes up for this reason.
4. FAULTY SENSORS
Since we’ve mentioned sensors, they also can cause a brake light warning to come up.
Sensors are the eyes and ears, so to say, of all of the vital systems on the car. Since they’re subdued to all kinds of harsh conditions, it’s inevitable that they fail over time, mostly because of material fatigue.
Also, sensors are meant to be replaced after a certain period of time,
When this happens, you can usually acquire an error code via the OBD scanner, find out which one is faulty and replace it.
But some caution is recommended since a faulty sensor can easily lead to a wild goose chase.
5. ABS SYSTEM MALFUNCTION
The ABS system is a marvel of automotive engineering and is responsible for saving millions of lives since it was invented.
But, as with any other system on the car, it can also malfunction, especially on cars with higher mileage or poorly maintained cars.
When you ask yourself why is my brake light on, I think that this is the rarest reason. The whole system on most cars is very well built and durable.
Most problems come from the mentioned sensors, punctured or broken brake lines, faulty electric installation, or else.
6. BLOWN FUSE
Another common reason when asking yourself why is my brake light on.
It’s perhaps the first thing you should check if the ABS light is on all the time.
The solution is very simple. Look at your car’s manual and see what the correct fuse is. If you see that it’s burnt out, replace it with one of the same amperage.
If you replace it and it burns out again, you probably have a more serious problem and you should check it out as soon as possible.
Always use a fuse with the recommended amperage, avoid replacing it with a higher amperage one. People do this because they think it will hold better and longer but can instead cause more damage or even a fire.
For a more thorough explanation on the whole subject, click here for a separate article on that topic or watch a video on our YouTube channel.
7. WIRING INSTALLATION OR CONNECTORS
This is a reason that can be harder to find.
Major hotspots for this problem are exposed parts of the installation, like under the car or inside the wheel arches.
Other places worth looking at are bending or stretching points like around the front wheels or places around the suspension.
Although the wiring is, in most cases, well-protected because of this exposure it’s prone to damage. The connectors are also susceptible to physical damage and above all rust.
A good example of this problem is the connector for the mentioned brake pad sensors. It’s usually attached to somewhere around the suspension strut and follows it when the wheels are turning to either side.
Over time, because of the motion and because of exposure to moisture, filth, or physical damage the connector can lose contact or the wires attached to it may break.
All of this will cause the brake light to come up.
8. PARKING BRAKE LIGHT SWITCH
On most cars that have a mechanical (not electrical) parking brake, there is a small switch at the base of the parking brake lever.
It’s a small simple switch that is engaged when the lever is raised.
Over time it may malfunction, mostly due to material fatigue or when the parking brake lever is continually slammed back into place.
When it malfunctions, the brake warning light is on all the time.
The replacement is simple and in most cases isn’t expensive. On some cars, it may be a problem to reach it since some trimming has to be removed.
9. BRAKE SWITCH
This is the switch that’s usually located above the brake pedal. It’s in charge of turning on the brake lights when you press the pedal.
When asking yourself why is my brake light on, know that this is one of the more common reasons.
After probably millions of times of switching on and off, it’s only logical that it will fail at one point mostly due to material fatigue.
Most problems come from burnt-out electric contacts or broken mechanisms inside the switch.
Besides turning on the brake light warning, it can also cause the brake lights to constantly be on or not even work at all.
10. ECU UNIT
The last and certainly the rarest reason is a damaged ECU unit.
You should consider this reason only if you’ve had serious trouble in the recent past with the electrics or electronics on your car.
One example would be if the car had alternator problems and it produced a higher voltage than normal. Another one would be a bad ground connection.
The tricky part about this reason is that it’s usually hard to spot since it may appear occasionally. Because of this, you may easily end replacing parts and making repairs that aren’t needed.
Perhaps the most important message of this whole article is: react to the problem on time!
Instead, of asking yourself all the time why is my brake light on, try to find the problem and solve it as soon as possible.
If you can’t do it or don’t have the time, drive the car to a mechanic.
Just don’t neglect it.
The brake system is perhaps the most important one on your car. Not tending to the problem can endanger both you, your passengers, and other participants in traffic.
Also, make a good and thorough diagnosis of the problem in order to avoid both unneeded repairs and future problems.
Written by: Sibin Spasojevic
Former car technician, life-long car and DIY enthusiast, author for Despairrepair.com