What is the reason for ABS light to come on?

The ABS warning light signals a fault in the anti-lock braking system. It appears when the vehicle’s computer detects a problem in wheel speed sensors, the hydraulic pump/modulator, wiring, or brake fluid level. In most cases you still have normal braking, but ABS and stability features may be limited until repaired.

What triggers the ABS warning light

The light activates when the ABS control module detects a fault in its monitored circuits. This can be caused by sensor or wiring problems, fluid issues, or faults in the ABS control hardware. The following sections break down the most common scenarios.

Common causes

Most ABS faults fall into a handful of categories. The following list covers typical culprits that trigger the warning:

• Faulty wheel speed sensor or tone ring (dirty, damaged, or misaligned)


• Damaged or corroded wiring or connectors to wheel speed sensors


• Blown fuse or faulty ABS relay


• Malfunctioning ABS control module or hydraulic control unit (pump/modulator)


• Low brake fluid level or brake fluid leaks


• A faulty brake light switch or pedal position sensor that affects ABS sensing

Because ABS relies on precise sensor data and hydraulic pressure, a fault in any of these areas will typically illuminate the warning light, and the system will revert to conventional braking without ABS.

Other factors that can trigger a warning

Additional situations that can cause occasional ABS warnings include:

• Recent battery disconnection, charging issues, or low voltage that briefly disrupts the ABS module


• Aftermarket wheels/tires or wheel alignment changes that affect sensor readings


• Extreme temperatures or moisture causing sensor corrosion or short circuits


• Software glitches or the need for module re-flash in modern vehicles

If you notice the light during or after any of these conditions, a diagnostic check is recommended to confirm the cause and prevent potential braking safety issues.

What to do if the ABS light is on

When the warning is active, here’s a practical checklist to follow before a shop visit:

• Check the brake fluid level and inspect for leaks; top up or repair as needed per the owner’s manual


• Inspect visible wiring around the wheels and brake components for damage or loose connectors


• Check fuses and relays for the ABS circuit and replace if blown, ensuring the correct rating


• Use an OBD-II scanner capable of reading ABS codes to retrieve Diagnostic Trouble Codes (DTCs) from the ABS module


• Record the codes and share them with a technician; avoid repeatedly clearing codes unless advised by a professional


• Drive cautiously and avoid hard braking until the system is inspected and repaired

These steps help identify whether the issue is simple (like a fluid level) or requires professional service for sensors, wiring, or the ABS module.

When to seek professional help

If the ABS light remains on after basic checks, or you notice abnormal braking behavior (soft pedal, pulsing brake force, or instability during braking), schedule service promptly. Modern ABS/traction control systems rely on complex diagnostics and specialized tools, so a qualified technician is best equipped to diagnose and repair the root cause.

Summary

The ABS warning light signals a fault in the anti-lock braking system and can be triggered by wheel speed sensor problems, wiring issues, a failing ABS module or pump, low brake fluid, or blown fuses. While regular brakes may still function, ABS may be disabled, reducing braking stability in emergency stops. A diagnostic check helps pinpoint the exact cause, enabling timely repair and a return to full braking performance.

Is it expensive to fix an ABS light?

Typical Repair Costs
ABS Sensors: $60 - $240, depending on the make and model of the vehicle. ABS Module: $240 - $720 for the part itself. Pump and Valves: $180 - $360, depending on the complexity.

How do I fix my ABS light?

To fix a glowing ABS light, first try simple fixes like restarting the car or checking and topping off the brake fluid. If that doesn't work, inspect the ABS fuse, clean the wheel speed sensors, or use an OBD-II scanner to diagnose specific codes. If the problem persists, a professional mechanic should perform a diagnostic test to identify a faulty sensor, module, or wiring. 
Basic troubleshooting
This video demonstrates how to perform a basic reset of your ABS system: 53sDIY with Michael BordersYouTube · Nov 17, 2019

• Restart your vehicle: Sometimes, simply turning the car off and on can clear a temporary glitch. 
• Check the brake fluid: A low brake fluid level is a common cause. Check the reservoir and add more if needed. 
• Inspect the fuse: Locate the ABS fuse in your vehicle's fuse box and check if it's blown. Replace it if necessary. 

Intermediate steps

• Clean the ABS sensors: Jack up the vehicle, remove the wheels, and clean each ABS wheel speed sensor. These can get clogged with dirt and debris. 
• Use an OBD-II scanner: Plug a scanner into your vehicle's diagnostic port to read the specific trouble codes. This can help pinpoint the exact issue, such as a faulty wheel speed sensor or a problem with the ABS module. 
• Disconnect the battery: As a more advanced step, disconnecting the battery for an hour or two can sometimes reset the system's computer. Reconnect it and see if the light goes out. 

When to call a professional

• If the basic and intermediate steps don't fix the problem, the issue could be a more serious electrical fault, a worn-out sensor, or a problem with the ABS control module itself. 
• If the ABS light and the brake warning light are both illuminated, your vehicle is not safe to drive and you should have it towed to a mechanic immediately. 
• A qualified mechanic has the tools and expertise to accurately diagnose and repair the underlying issue. 

Is it okay to drive with an ABS light on?

It is not recommended to drive with the ABS light on because it indicates a malfunction that compromises safety, though your regular brakes will still work. You can drive cautiously over short distances, but avoid sudden stops, especially in bad weather, and get the system checked by a mechanic as soon as possible. If both the ABS and brake warning lights are on at the same time, do not drive and have the vehicle towed to a mechanic, as this indicates a more serious problem with your primary braking system. 
Driving with the ABS light on 
This video explains the function of the ABS system and what happens when the warning light is on: 1mTorqueCarsYouTube · Apr 9, 2023

• Your regular brakes still work: The ABS system is separate from your standard braking system. You can still slow down and stop your car, but the anti-lock feature will be unavailable. 
• Risk of skidding: Without ABS, your wheels could lock up during an emergency stop, which could cause you to lose steering control and increase stopping distance, particularly on slippery surfaces like wet roads, snow, or ice. 
• Other systems may be affected: The ABS system is connected to other safety features like electronic stability control. A fault could cause these systems to behave unpredictably or stop working altogether. 

What to do

• Avoid hard braking: Drive more cautiously, leave more space between your car and others, and avoid sudden or heavy braking. 
• Check for a second warning light: If the standard brake warning light is also on, this signifies a problem with your regular brakes, which is a much more serious issue. In this case, stop the car immediately in a safe place and have it towed. 
• Get it serviced: If the ABS light stays on, have a mechanic inspect the vehicle to diagnose and fix the issue. Potential causes include faulty sensors, low brake fluid, or problems with the ABS control module. 

Why is my ABS and brake light on but my brakes work fine?

The ABS and brake lights can come on even if your brakes feel fine because a problem with a component related to the braking system, like a wheel speed sensor, can trigger the warning lights. Other causes include low brake fluid, a bad wheel bearing, or a faulty ABS module. To properly diagnose the issue, you will need to scan the car for trouble codes, as this can pinpoint the specific problem.
 
You can watch this video to learn how to diagnose wheel speed sensors: 13s1A Auto: Repair Tips & Secrets Only Mechanics KnowYouTube · Jan 7, 2021
Common causes

• Wheel speed sensor: This is a very common culprit. If a sensor is malfunctioning, its wire is broken, or the tone ring it reads is damaged, the computer will detect a discrepancy and trigger the lights. 
• Brake fluid level: Low brake fluid can be a sign of a leak or worn brake pads. A sensor in the brake fluid reservoir can trigger the brake light, and sometimes the ABS light as well. 
• Bad wheel bearing: A failing wheel bearing can interfere with the wheel speed sensor's ability to read the correct speed, causing the ABS light to come on. 
• Faulty ABS module: The ABS module is the "brain" of the system. If it's malfunctioning, it will trigger the warning lights and may need to be replaced. 
• Blown ABS fuse: A blown fuse can also cause the ABS light to illuminate. 

This video explains the importance of wheel bearings in ABS system: 46s1A Auto: Repair Tips & Secrets Only Mechanics KnowYouTube · Apr 8, 2023
What to do

1. Check brake fluid: Inspect the brake fluid reservoir. If the level is low, top it off and monitor it closely for any further drops. If it's consistently low, have your brake system inspected for leaks. 
2. Scan for codes: A diagnostic scan tool is the best way to find the exact problem. It can read the specific trouble codes stored in the ABS computer, which will point you toward the faulty sensor or component. 
3. Check the ABS fuse: Consult your owner's manual to locate the ABS fuse and check if it is blown. 
4. Professional inspection: If you can't find the cause or don't have a scan tool, a mechanic can perform a comprehensive inspection and diagnosis for you.