The ABS light on your dashboard serves a handful of extremely important purposes. It turns on every time you start your car to let you know it’s still working, and it will come on again if there are any problems with your anti-lock braking system. In some cases, your ABS light can even blink out trouble codes to help narrow down the source of a problem. In other situations, especially when the ABS light isn’t the only dash warning light to illuminate, it may be a warning that your car won’t be safe to drive until repairs are made.
What is an ABS Light?
The ABS light in your car or truck is a dash warning light that is specifically tied into the anti-lock brake system. These lights are usually amber in color, although they can also be yellow, orange, or even red in some applications. They typically look like the letters ABS surrounded by two circles, with the top and bottom of the outer circle cut off. In other applications, the light will consist solely of the letters ABS.
The anti-lock brake system, in turn, is responsible for pulsing your brakes under very specific circumstances. If the ABS system determines that your wheels are in danger of locking up, it is capable of rapidly activating and deactivating individual brake calipers or wheel cylinders.
The point of rapidly pulsing the brakes is to avoid a skid, because an uncontrolled skid both increases the stopping distance and may result in a total loss of directional control.
In most driving conditions, this means that a functioning ABS system helps reduce stopping distance, while also helping you maintain control of your vehicle during an emergency.
If there are any problems with your ABS system that might prevent it from performing those functions, the ABS light will illuminate.
Some problems will cause the light to illuminate temporarily, while others will cause it to remain on until the issue is addressed.
What Causes an ABS Light to Come On?
The two reasons for an ABS light to come on are to test the function of the bulb or to warn the driver that some type of fault has occurred in the anti-lock brake system.
Some of the common reasons for an ABS light to come on include:
Standard bulb check
Faulty control unit
Bad speed sensor or wiring problem
Failed or failing pump
What to Do When Your ABS Light Comes On
Since there are so many reasons that an ABS light can come on, the best way to deal with the situation depends on a number of factors. For instance, if you notice that the light comes on when you start your vehicle, and then it turns off, you don’t have to do anything. This is commonly known as a “bulb check,” and it happens so that you know your warning lights are all working properly.
If you notice that your ABS light, or any other warning light, doesn’t come on when you first start your car, you will need to check to see if the bulb is burned out. Burned out dash warning lights should be replaced immediately. If a warning light like your ABS light is burned out, you’ll have no way of knowing when a problem occurs.
If your ABS light comes on when you’re driving, that means that some type of fault has been detected in the system. It also means that the ABS system may not work properly if you end up in a panic stop situation and you should operate under the assumption that you will not be able to count on the anti-lock brakes to help you stop or maintain control of your vehicle.
In most circumstances, it’s perfectly safe to continue driving if your ABS light comes on. However, it’s important to remember that there are several systems that rely on ABS to function. So if your ABS system isn’t working properly, you may not be able to count on your traction control, stability control, or other related systems.
This is why it’s so important to pay attention to how your vehicle is handling, and braking, and make an educated decision on whether to drive to a repair shop or call for a tow.
ABS Components You Can Check Yourself
Most anti-lock brake repairs and diagnostic work require special tools and knowledge not easily available to most drivers. However, there are a few things you can do with more basic tools to help ensure your safety if you notice that your ABS light has come on.
Some vehicles have a separate brake fluid reservoir for the anti-lock brake system, while others use a single reservoir. In either case, checking the brake fluid level is one easy thing that you can do yourself. If the level is low, you can top it off yourself, but it’s extremely important to use the right type of fluid, and to only use brake fluid from a container that has just been opened.
Safely Adding Brake Fluid to an ABS System
Before you add any brake fluid to your ABS reservoir, or the main reservoir, it's important to find out what type of fluid your vehicle uses. This information will typically be stamped or printed right on the reservoir, or the reservoir cap. If it isn't, then you may find it in your owner's manual, or on the vehicle specifications sticker in the engine compartment.
Some types of brake fluids aren't compatible with others, which is why it's so important to use the right type. For instance, if you top your brake fluid reservoir off with silicone-based DOT 5 brake fluid, and your vehicle uses polyethylene glycol-based DOT 3 brake fluid, you can end up damaging internal seals or ABS components.
In the same vein, adding DOT 3 fluid to a DOT 4 system can cause problems due to the lower boiling point of DOT 3 brake fluid.
The reason that you shouldn’t use a previously opened bottle that has been sitting around for awhile is that brake fluid is hygroscopic. That means it will tend to absorb moisture from the air, and any moisture present in your brake fluid can lead to a soft pedal and make it harder to stop.
Performing Other Visual ABS Inspections
If you are able to locate and identify your ABS control unit and pump, you can check to make sure that they are plugged in tight and that the electrical connections are free of contamination or corrosion. You may also want to check the ABS fuse.
Another thing you may be able to check yourself is whether the wheel speed sensors are screwed in tight, plugged in, and free of contaminants. These sensors are installed in the hubs of each wheel, so you may have an easier time seeing the front ones by turning your wheels all the way to the left or the right. The rear ones may be difficult to see unless you drive a vehicle with decent ground clearance.
Further diagnostics, like testing the operation of individual wheel speed sensors, requires specialty tools. For instance, you may be able to test a wheel speed sensor for an internal short with any basic ohmmeter, but a scan tool is tremendously useful to check the outputs from the sensors.
Checking ABS Trouble Codes
In some cases, you can access ABS codes manually without any special tools.
For this to work, the computer in your car has to be capable of flashing the ABS light. The procedure usually starts with locating your vehicle's data connector, which is the same connection used by code readers and scan tools.
Each vehicle has a specific way to manually check for ABS trouble codes, so it's important to look up the right procedure before you attempt this. In many cases, you will have to use a jumper wire to connect two specific terminals in the data connector. This instructs the computer to enter a self-diagnostic mode, and the ABS light will flash.
By counting the number of times the ABS light flashes, it's possible to determine the code, or codes, stored in the computer.
While that is sometimes an option, reading ABS trouble codes with a scan tool is both easier and less prone to accidentally identifying the wrong code. This is technically something you can do at home, but most ABS diagnostic and repair work is better left to qualified professionals.
For instance, you may be able to learn that your car has stored a speed sensor code, but that doesn't mean replacing the speed sensor will fix the problem. The speed sensor might be bad in that situation, but a thorough diagnostic would rule out other possibilities before coming to that conclusion.
Is it Safe to Keep Driving With an ABS Light On?
If you’re ever unlucky enough to have your ABS light come on when you’re driving, the most important thing to remember is to keep a level head. The last thing you want to do is panic the moment you see a warning light illuminate on your dash.
In most situations, it is perfectly safe to continue driving with the ABS light on. If the brake pedal seems to work normally, you should be able to continue driving until you are able to take your vehicle to a repair shop or check out the anti-lock brake system yourself.
While an ABS light isn’t the type of problem you can ignore indefinitely, and you should get it checked out as soon as possible, your vehicle will typically continue to operate as if it didn’t have anti-lock brakes at all.
That means if you find yourself in a panic stop situation, you will have to pump the brakes yourself, and the wheels may even lock up. If that happens, it’s vital to know how to safely recover from a skid, or you may suffer extreme damage to your vehicle or great personal injury.
There are exceptions where you shouldn’t drive your vehicle at all. For instance, if both your ABS light and normal brake warning light illuminate at the same time, that may indicate a more serious problem, like catastrophic fluid loss. In that same vein, if your brake pedal doesn’t feel right when you attempt to slow down or stop, it’s always better to err on the side of caution.