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What To Do If Your ABS Warning Light Comes On


The anti-lock braking system, better known as the ABS system makes sure your tires continue to stick to the road while you’re braking. If your tires lose contact with the road, your car can end up skidding which as you might guess, is bad.

It’s commonly assumed that the ABS helps stopping distance, but this isn’t necessarily true. The main function of the ABS system is to prevent your car’s wheels from locking up, especially when driving in challenging conditions, which can cause skidding.

With that being said, let’s clue you in on a few other little quirks of the ABS light before we move on to talking about some of the more complicated issues.

The Anti Lock Braking System Has Been Around For Awhile

Anti-lock braking has been around since the early days of automobiles, with the first true ABS systems dating back to the 1920s. However, it wouldn’t be until almost 60 years later that it would become more commonplace.

As automobile regulation began to catch up with technology in the 80s and early 90s, anti-lock braking systems became more common as part of an initiative to produce safer and more responsive vehicles.

Although today driving is remarkably safe, that wasn’t the case back when ABS systems were first invented.


Anti-skid or anti-lock braking first became more commonplace on cars and trucks in the early 1980s and 1990s as a positive step toward improved safety and vehicle control during hard braking in slippery conditions.

How Does The ABS System Work?

abs module inside car

Although ABS seems complicated, it’s actually quite simple in function. If you encounter a skid while braking, the ABS control module senses a slowdown or pause in wheel rotation, modulating brake application to help you steer out of trouble. In a conventional skid, steering control is lost and the vehicle continues to travel in the direction of the skid. Then, anti-lock braking pulses the brakes, which results in an improved measure of control out of the skid.

A typical ABS consists of four wheel sensors (sometimes two or three), an anti-lock electronic control module and a hydraulic control unit. Under normal conditions, this system applies master cylinder hydraulic pressure to all four brakes, and pulsing pressure to each brake when a skid is detected.

It’s Normal For Your ABS Light To Briefly Flash When You Start The Car

abs dashboard light on

Your ABS system conducts a self-check every time you start the engine. Once you start the engine, the ABS light should briefly flash on the dashboard. This is normal, and shows that the ABS system is checking itself as it’s supposed to.

Again, it’s completely normal for the ABS Warning Light to come on and off in this way, and it usually lasts for about 2-4 seconds, depending on your vehicle. It’s when the ABS light stays on longer than this that we have a problem.

Depending on the car you have, you may also experience:

  • A clunking noise during the ABS test. This is the sound of your ABS system engaging and disengaing.
  • The brake pedal pulsating, which is reaction of your ABS system engaging and disengaging.
  • You should still have normal braking controls if your ABS system is disabled or disengaged.

It’s Not Normal For Your ABS Light To Come On While You’re Driving

it's not normal for your dashboard light to come on while driving

It’s when the ABS light comes on during normal driving that you should be concerened. This means that the ABS system is not working properly.

Your brakes should still work normally, but the ABS system may not engage if you need to make an emergancy stop. Ideally, you’ll want to have a mechanic take a look at your car with an OBD-II reader as soon as possible to diagnose any issues.

It’s Safe To Drive Carefully With The ABS Light On. But Get It Looked At Quickly.

mechanic wearing a mask with oil quart

You can still drive the car with your ABS light on, because it does not impact normal braking. However, we wouldn’t recommend you do this because your ABS system helps to control stopping, and it can be dangerous to be driving without it. When things go wrong, you want to know how your vehicle is going to perform. Without your ABS system working properly, your vehicle may not handle like it’s designed to handle under heavy braking.

We reccomend that you get your ABS light looked at as soon as it comes on.

There Are A Number Of Reasons Your ABS Light May Come On

If you don’t have an OBD-II reader handy, you can be reasonably confident that one of the following conditions is causing your ABS light to come on.

Of course, we recommend taking your car to a licensed mechanic to get a specific diagnosis, but this can serve as a good starting point.

1: Bad ABS Module

real abs module

The ABS module itself can also go bad. Typically this is associated with the wiring. What normally happens is one (or multiple) wires go bad due to corrosion. This then leads to delays in communication (or no communication at all) between the wheel speed sensor and the ABS module.

In the best case scenario, your car will just need a bit of rewiring. In the worst case secnairo, you’ll need a full ABS module replacement which can be pricey.

Symptoms of a bad ABS Module:

  • Brakes become less responsive over time. It starts slowly at first, but will get worse over time to the point where the brakes may not work at all. When the brakes stop working, usually the module is completely broken.
  • Brake pads become more difficult to push over time.
  • Brakes may lock up, even during normal driving. If you are experiencing this, take your car to the mechanic immediately.
  • Random clicking noises from your brakes when stopping, or brakes pumping as you stop.

2: Low Brake Fluid

low brake fluid in brake fluid resiviour

Your ABS module relies on hydraulic brake fluid which is driven through a cylinder in order to make your brakes work. Without this brake fluid filling the brake reservoir, bad things happen.

A low level of fluid can cause the ABS light to come on. This can be caused by a leaky fluid reservoir, a leaky seal, or air in the system. It can also be caused by worn brakes, which we’ll talk about more in a minute.

Without fluid in the system, your ABS module won’t be able to evenly balance the brake pressure on each wheel which can cause skidding and other issues.

Symptoms of low brake fluid:

  • The brake pedal is less responsive than usual. You may notice it’s harder to actually brake.
  • Noisy brakes. You may notice a scraping sound or a grinding that’s similar to worn brake pads.

3: Faulty Speed Sensor

abs wheel speed sensor real

Your wheel speed sensor’s job is to record the actual speed of your car’s wheels and then report that speed back to the electrical control unit (ECU). The ECU helps to control multiple systems in your car, including your ABS system.

When the ECU detects that one wheel is moving slower than the others, it release break fluid to allow that wheel to move at the same speed as the other wheels, which helps your car continue to grip the road.

However, if the speed sensor is not working, the ECU won’t be able to get this data, and as a result, your ABS light will come on.

Because the speed sensor is typically located close to the wheels (as this speed sensor is different than the one in the transmission), it can be damaged by the high heat of the brakes. It’s also possible for the sensor to be destroyed by debris, or metal shavings from the brakes.

Symptoms of a faulty speed sensor:

  • Traction control light is on, even if you didn’t turn it on.
  • Car takes longer to stop, even if the ABS light isn’t on.
  • Car loses traction when braking hard.

4: Bad Hydraulic Pump/Unresponsive Valve

bad hydraulic pump

The ABS system controls brake fluid pressure through a hydraulic pump. The pump itself applies brake fluid through a cylinder in order to control the brakes during normal braking.

The ABS system then can lower the brake pressure on indivdual wheels based on the speed reading the ABS module is getting from the speed sensor.

In a perfect world, this all works seamlessly. However, if the hydraulic pump isn’t working correctly, or if there’s a damaged hydraulic valve, the whole thing can be blown to hell really quick.

It’s normal for the pump to wear over time, and this can be caused by dirt or by metal shavings in the brake fluid. It can be easy to prevent this if you have your brake fluid checked whenever you have your brakes done.

Symptoms of a bad hydraulic pump/unresponsive valve:

  • Poor braking performance. Slow to stop, and it gets worse over time.
  • When a master cylinder begins to fail, sometimes the brakes will feel fine one second and lose braking power the next. If the fluid is leaking past the seals inside the cylinder, the pedal may feel firm for a moment but won’t hold steady; it’ll feel spongy and keep sinking towards the floor.
  • If you notice brake fluid leaking from the back of the cylinder against the firewall or brake booster, or can see it leaking down the firewall on the inside of the car, it’s definitely time to have the master cylinder replaced. If it’s leaking, it’ll run out of fluid eventually, leaving you without at least half your brakes. Plus, it lets air enter the system, causing the brakes to feel spongy as well. Sometimes the pedal will regain firmness if you pump it a couple of times, but it typically won’t last for more than a few seconds.

5: Blown Fuse

man holding blown car fuse

Just like all electrical components of your car, the ABS has its own fuse. And as fuses sometimes do, they go bad. Considering how easy it is for a fuse to blow, it’s worth it to check the fuse box before doing anything else.

Symptoms of a blown fuse:

  • ABS light goes on suddenly without any of the other symptoms listed here.

To Be Clear, Worn Brakes CAN Cause The ABS Light To Come On, But It’s Not Why You Think

slightly worn brakes

Your brakes and your ABS are not the same, even though they work together. Your ABS system has its own electrical control unit which is separate from your braking system, even though the ABS and your brakes work together.

In about 90% of cases, your ABS light is not caused by worn brake pads. Your brake pads have no bearing on whether or not your ABS system will work. Remember, all the ABS does is control the pressure on your brakes. It can control the pressure even with worn brakes.

Granted, it will be harder for the ABS system to control the wheel speed with worn brakes though, which leads me into my next point. If you leave your worn brakes on for some time and continue braking aggressively, your worn brakes CAN cause your ABS system to wear down in tandem.

There are a couple of ways this can happen.

The most common is for metal shavings from worn brake pads to cause damage. Metal shavings can damage the speed sensors, wiring, etc. The heat from the metal on metal on worn brake pads on the wheel can also cause the speed sensor to get damaged as well.

The other way it can happen is through your worn brake pads depleting your brake fluid. When your brake pads are worn down, the caliper piston is forced to travel farther to the brake pads, away from the housing. This requires more brake fluid to travel further down which may become depleted over time.

As you might imagine, low fluid can cause your ABS light to come on.

So again, while your worn brakes may not directly cause your ABS light to come on, if you ignore your worn brakes for long enough, it’s possible that they will cause your ABS light to come on.

The Cost Of Fixing Your ABS Light Issue Varies A Lot

The cost of fixing your ABS light is going to vary depending on what problem you have.

Rather than giving you a broad estimate, I’m going to give you the rough cost of repair for the 5 major ABS issues I mentioned above. Sound fair to you?

ABS Issue Cost To Fix How Common Is This Issue?
Blown Fuse ~$20 Common
Bad ABS Module $200-$550 Uncommon
Bad Hydraulic Pump / Frozen Valve $300-$450 Rare
Fauly Speed Sensor $100-$200 each Common
Low Brake Fluid ~$50 Uncommon

Depending on what goes wrong, you could be looking at anywhere from $20 bucks or so, all the way up to $1,000+ if a bunch of parts fail at once.

In my 20 years as a mechanic, I can tell you that the average ABS repair does not often cost more than $500 dollars, so if you’re getting an assessment above that, you may want to ask some questions.

Resetting Your ABS Light Without A Scan Tool Is Possible, But It’s A Pain In The Butt

mechanic using obd-ii reader
You really want to get an OBD-II reader. It helps.

It is possible to reset the ABS light without the use of a scanning tool. However, it’s a pain in the ass. You’re really better off spending the $20 bucks to buy an OBD-II reader. There is so much variance between how to reset the light on each car. In fact, the process can even vary in different model years of the same vehicle.

You will need a fused jumper wire or service connector to do this manually. Go through the following steps to reset:

  1. Find the DLC on your vehicle. If you don’t know where to find it, a quick web search will do the trick.
  2. Connect the two fuses on the DLC. Turn on the ignition but do not start the engine. You will see the ABS light flash.
  3. Press the brake pedal until you hear a click. Push it 8 times as quickly as possible.
  4. If successful, the ABS light will quit flashing, come back on, and then flash on about 4 times.

Seriously, just spend the $20 bucks and buy an OBD-II reader. It’s less complicated than trying to reset the light manually. It’s plug and play and as easy as can be. If my 89-year-old grandmother can use it, you can use it too.

And It’s Worth Resetting Your Light Because Your Car Won’t Pass Inspection With It On

The ABS system is a safety system – and if your car is having a safety inspection, it won’t pass if the ABS light is on.

So get it fixed.

Not all states have safety inspections, however. Some states only do VIN and Emissions inspections, which your car won’t fail if your ABS light is on because the ABS light has no bearing on those systems. For more information on inspections in your state, check this article out.

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