ABS Failure: Symptoms, Costs and How to Fix

When the ABS system stops working, braking becomes a lot riskier. Especially on wet surfaces or when you brake at high speeds. So if you notice the ABS warning light staying on, a pulsing brake pedal, longer stopping distances or brakes that feel unusually unresponsive, you have a (potentially) big issue. 

Fixing an ABS fault costs anywhere from £50 for a simple fluid top-up or flush to £900 or more if the ABS module needs replacing. The exact cost depends on your car’s make, model and the specific part that’s failed.

So what causes ABS failure? What are the signs to look out for? How do I fix it? Is it even worth fixing?

I’ll answer all those questions and more in this complete guide.

What is the anti-lock braking system (ABS)?

The anti-lock braking system (ABS) is a critical safety feature that keeps your wheels from locking up during hard or sudden braking. This gives you extra steering control and stability in these scenarios, which reduces the risk of skidding or losing control.

Its key components are:

• Wheel speed sensors monitor each wheel’s rotation speed.
• ABS control module (ECU) processes signals and manages brake pressure.
• Hydraulic modulator (ABS pump) adjusts brake pressure to prevent lock-up.
• Valves regulate brake fluid flow to each wheel.
• Brake lines carry hydraulic pressure from the master cylinder to the brakes.

The system works by pulsing the brakes 15-20 times per second (too fast for you to feel individually) when it detects a wheel about to lock up. This allows the wheels to keep rotating while still applying maximum braking force. 

In modern cars, ABS is standard and works alongside traction control and electronic stability systems to keep you safe. And it’s particularly important when you’re driving on wet, icy or uneven roads and when you have to brake suddenly at high speeds.

What are the symptoms of ABS failure?

When your ABS starts to fail, you’ll notice the ABS light staying on, brakes locking under hard stops, weird noises or the pedal feeling jittery or unresponsive.

In some of these cases, the brakes will still work, just without the safety net of anti-lock protection. That means that stopping distances are longer and control is less predictable.

ABS warning light

The first thing you’ll notice.

If the ABS warning light comes on and stays lit on your dashboard, it means the system detects a fault and has switched itself off. You’ll still have normal braking, but the anti-lock function won’t activate if you brake suddenly or on a slippery surface.

There are quite a few reasons this could happen:

• Faulty wheel speed sensors
• Damaged or dirty sensor wiring
• Low brake fluid level
• Blown ABS fuse or relay
• Faulty ABS pump or hydraulic unit
• Malfunctioning ABS control module (ECU)
• Worn brake pads affecting sensor readings
• Air trapped in the brake lines after service

When this happens, the first things you should do are check your fluid levels and the ABS fuse to rule out the basic problems. If you see any obvious damage or the light stays on after you’ve checked those things, get it checked at the garage.

Unresponsive brake pedal

If the brake pedal feels soft, sinks too easily or takes longer to engage, it sometimes points to a problem with the ABS system. A failing pump or air trapped in the hydraulic lines sometimes reduces brake pressure, making the pedal unresponsive and increasing your stopping distance.

If the pedal's not responding:

• Get over to a safe location using the emergency brake (and downshifting if you have a manual transmission).
• Check your brake fluid level and inspect the floor mats for obstructions.

If the fluid levels are fine and there’s nothing blocking the brake pedal, it’s probably a bigger issue and you should take it to the mechanic ASAP.

Loss of traction

The ABS helps you stay in control when you’re braking, so a noticeable loss of traction during hard braking is one of the clearest signs the anti-lock braking has switched off.

To tell if it’s related to ABS failure rather than a separate issue, watch for:

• The ABS light staying on
• Brakes locking under pressure
• A lack of the usual pulsing vibration in the pedal when braking hard

If those three symptoms appear together, it’s almost always an ABS failure rather than a tyre or suspension issue.

Unusual noises

Even if you don’t have any noticeable performance problems, you might still notice strange sounds coming from the braking system. These are also signs of ABS failure.

• Grinding or rattling usually signals internal wear or damage within the ABS module or hydraulic unit.
• Whining or buzzing can mean the ABS pump motor is struggling to operate, possibly due to poor lubrication, a stuck relay, or internal failure.
• Clicking often indicates faulty sensors or a misfiring hydraulic pump.

These noises (particularly grinding or rattling) naturally happen during emergency stops. That’s normal. But if they happen during regular braking, it’s a clear sign something’s wrong and you should have a mechanic look at the system right away.

What causes the ABS to fail?

Anti-lock braking system failure usually comes down to one of five common problems: faulty wheel speed sensors, a damaged ABS pump, a failed control module, low brake fluid or electrical and wiring faults. Each of these issues affects how the system monitors and regulates brake pressure. Some are simple fixes; others are expensive and complicated.

Let’s look at each cause in more detail to understand what goes wrong.

Faulty wheel sensors

Wheel speed sensors sit at each wheel and measure how fast they’re turning. This is how the ABS knows when a wheel is about to lock up.

If a sensor is covered in dirt or debris, its connectors are corroded, the wiring is damaged or there’s wear and tear from age and harsh driving conditions, it’ll send incorrect readings (or no readings at all). Then, the system can’t adjust brake pressure correctly.

How to spot a failing wheel sensor:

• Your speedometer fluctuates or shows erratic readings.
• The traction control or stability control lights come on with the ABS light.
• You feel the brakes pulse or grab when driving normally.
• The ABS doesn’t engage during hard or sudden stops.

Damaged ABS pump

The ABS pump’s job is to maintain the correct brake pressure whenever the system activates. It rapidly increases or releases hydraulic pressure to prevent wheel lock-up.

If the pump becomes damaged or seizes, the system can’t modulate that pressure effectively. This means the ABS can’t step in when you need it most, leaving you with standard brakes that may skid under hard braking.

How to know if it’s a damaged ABS pump:

• The ABS warning light stays illuminated even after you restart the car.
• The brake pedal feels unusually stiff or vibrates when pressed.
• You hear a persistent buzzing or clicking sound from the engine bay.
• Braking responsiveness becomes inconsistent.
• Diagnostic scans show “ABS pump motor” or “hydraulic unit” error codes.

Faulty ABS control module (ECU)

The ABS control module is the brain of the anti-lock braking system. It constantly processes signals from the wheel sensors and tells the pump and valves how to adjust brake pressure in real time.

When there’s electrical issues, internal corrosion or a software glitch, it can’t send the right signals to control the pump or hydraulic valves.

Common symptoms of a faulty ABS control module:

• Multiple braking lights turn on.
• Speedometer readings are incorrect.
• Brakes lock up even in normal driving conditions.
• Brake pedal requires more effort when you press on it.
• Fault codes appear during diagnostic checks for “ABS module” or “communication failure”.
• In severe cases, the entire ABS and traction control system stop working.

Low brake fluid

Brake fluid is what transfers the pressure from your foot on the pedal to the brake system itself. When fluid levels drop too low, air enters the system, which reduces hydraulic pressure. Since the ABS relies on that hydraulic pressure to modulate braking force, even a small drop stops the system from activating correctly.

How to check and maintain brake fluid levels:

1. Park on a flat surface and switch off the engine.
2. Locate the brake fluid reservoir under the bonnet (it’s usually marked with a yellow cap).
3. Check that the fluid level sits between the “MIN” and “MAX” lines.
4. If it’s low, top it up with the correct brake fluid type listed in your car’s manual.
5. Avoid overfilling and always replace the cap tightly.

Keeping brake fluid topped up and fresh (it should be replaced every two years) helps maintain full ABS functionality and prevents costly pump or module damage.

Wiring and electrical issues

The ABS system depends on a network of sensors, relays and control units. These are all connected by electrical wiring. If any of them are damaged, corroded or loose, the system gets faulty data or loses power entirely.

This is most common in older cars where wiring has been exposed to years of vibration, moisture and road salt. If the ABS light flickers on and off or there’s a total system shutdown during braking, this is probably the root cause.

To troubleshoot electrical issues:

• Check fuses and relays. A blown fuse or bad relay can cut power to the ABS module.
• Inspect wiring harnesses. Look for frayed wires, corrosion and loose connectors near the wheels or ABS unit.
• Use a diagnostic scanner. It’ll pinpoint which sensor or circuit is causing the fault.
• Test battery voltage. Low voltage or weak grounds can affect ABS performance.
• Consult a professional. If the problem persists after basic checks, a mechanic can run continuity and resistance tests to trace the fault accurately.

How much does it cost to fix ABS failure?

Fixing ABS failure will run you anywhere from £50 to over £900. It all depends on what the issue is. A simple top-up or sensor replacement sits at the low end, while repairing or replacing the ABS pump or control module pushes costs far higher. Labour time, parts availability and your vehicle’s make also play a big role in the final bill.

Below, I’ll break down what you can expect to pay for different ABS repairs.

Average cost of ABS repair in the UK (2025)

To clarify that cost range a little, I’ve created a table you can use as a general guide to current ABS repair costs in the UK.

ABS repair costs vary so much because no two systems are exactly the same. Modern cars use intricate electronic and hydraulic setups that are time-consuming to diagnose and repair. Older ones have simpler components.

Labour costs also depend on how difficult it is to access the part. For instance, the front wheel sensors are pretty easy to reach in most cases but replacing a pump or module takes several hours.

On top of that, prices differ between makes and models, with premium brands and newer systems costing more for both the OEM replacement parts and labour.

Factors affecting ABS repair costs

Several factors influence how much you’ll pay to fix an ABS issue.

• Type of fault: This is the biggest one. A single sensor replacement is quick and cheap (about £100 to £150). Replacing a hydraulic pump or ECU requires more parts and labour.
• Vehicle make and model: Luxury and newer cars use proprietary components that cost more to replace. Older cars have parts that are easier to access, like external centric rings.
• Labour rates: These vary by region and garage. Plus, diagnosing the issue adds to the total if the mechanic needs to use advanced scanning tools.
• Additional wear: If your ABS problem has caused additional wear, like air in the brake lines or corrosion in connectors, you’ll spend extra on repair work beyond the core fix.

Should you repair or scrap your car?

The question I get asked the most. Is my ABS failure even worth repairing? The answer depends on a few things:

• What your car’s currently worth
• How many years it realistically has left
• The total cost of repairing the ABS
• Other repairs on the horizon

If your car is relatively new, in good condition and worth well over the repair cost, then fixing the ABS is almost always worthwhile. You’ll get plenty of useful years out of it and, assuming you’re using OEM parts, a decent resale value as well.

But if it’s an old car with high mileage and other mechanical problems, paying several hundred pounds for ABS repairs doesn’t make any financial sense.

When to consider scrapping your car

You should scrap your car at an ATF if the ABS repair costs more than 50% of the car’s current market value. Also consider if it’s old, high-mileage or unreliable overall and nearing that 50% threshold.

Even if the car doesn’t meet the ‘50% Rule’, do the math. If it needs other expensive repairs now or in the future, like suspension, gearbox or engine work, does that push total costs past the car’s value?

If the answer’s “yes” or “probably”, scrap it.

How to fix ABS failure

Because ABS is a critical safety system, it’s best handled by a qualified mechanic who can properly test, replace and bleed the system to restore full braking performance.

When you take it to the garage, here’s what they’ll typically do:

1. Run a diagnostic scan. They’ll use an OBD2 scanner to read ABS fault codes and pinpoint whether the issue is with a sensor, pump, module or wiring.
2. Inspect wheel sensors and wiring. The mechanic checks each wheel sensor, tone ring, and harness for things like dirt and corrosion. They’ll also note physical damage.
3. Test the ABS pump and control module. They confirm the pump is getting power, listen for operation and test the ECU for internal faults or communication errors.
4. Check brake fluid and the hydraulic system. Low fluid levels, fluid that’s contaminated, air in the system and leaks are all tied to ABS performance. They look at everything here so no stone is left unturned.
5. Replace faulty parts. Whether it’s a sensor, pump, module or something else, they’ll install the correct replacement part (make sure it’s OEM or a very high-quality aftermarket).
6. Bleed the brakes and reset the system. After repairs, they’ll bleed the hydraulic system. Once that’s done, they’ll perform a scan-tool guided ABS bleed (if required) and clear the fault codes.
7. Road test the vehicle. Finally, they verify the ABS activates correctly, the warning light stays off, and braking feels stable and responsive.

How to prevent ABS failure

Maybe it goes without saying, but prevention is far better than a potentially expensive repair. A few basic steps will keep you from ever worrying about a broken anti-lock braking system in the first place.

Perform regular brake system maintenance.

Regular maintenance keeps your whole braking system working as it should. Small checks now prevent costly failures later on.

My quick ABS maintenance tips:

• Check your brake fluid every few months and top it up if it’s near the minimum line.
• Replace brake fluid every two years to prevent moisture buildup that can damage sensors and pumps.
• Inspect brake pads and discs regularly for wear, as uneven braking can trigger ABS faults.
• Keep wheel speed sensors clean by washing away mud, grime, or salt after winter driving.
• Have a full brake system inspection during every service to catch electrical or hydraulic issues early.

Keep the wheel sensors clean and free of debris.

Wheel sensors are exposed to dirt, mud and salt every time you drive. Eventually, that buildup blocks the sensor’s ability to read wheel speed correctly. That can trigger ABS warnings even when the system itself is fine.

To keep that from happening:

• Clean around each wheel hub when washing your car, especially after driving in mud or snow.
• Avoid using high-pressure water directly on sensors or wiring.
• If the ABS light comes on after driving in harsh conditions, check for mud or corrosion before assuming a major fault.
• During servicing, ask your mechanic to inspect and clean the sensors as part of the brake check.

Monitor ABS warning lights and act promptly.

The ABS warning light is your first and most reliable indicator something’s wrong. Ignoring it will turn a minor sensor issue into a major repair later.

Not to mention, you never want to ignore the ABS light because, regardless of the problem, it means the ABS is switched off and therefore will not work when you brake. So your car is unsafe to drive.

Start by using an OBD2 scanner to check for stored fault codes if you have one. And if traction control or brake system warnings appear alongside the ABS light, book a diagnostic check immediately.

Ensure proper wheel alignment.

Misaligned wheels put extra strain on sensors and can cause uneven readings, which trigger warning lights and disable the anti-lock braking.

These basic steps will help you avoid this:

• Have your wheel alignment checked at least once a year or after hitting a pothole or curb.
• Watch for signs like uneven tyre wear or the car pulling to one side while braking.
• Keep tyres inflated to the recommended pressure, as incorrect levels can also affect ABS sensor readings.
• During alignment checks, ask your garage to inspect sensor brackets and wiring for damage or corrosion.

Use quality replacement parts.

When repairing your ABS, always choose OEM parts. They’re designed specifically for your car, tested to meet safety standards and usually come with a warranty. While they cost more upfront, they’ll protect your car’s resale value and reduce the risk of recurring faults.

To make sure OEM is what you get:

• Ask your mechanic to source OEM or premium-brand parts for any ABS repair.
• Keep receipts and part numbers for future resale or warranty claims.
• Remember: saving a few pounds now can lead to much higher costs if a low-quality part fails again.