Why would my ABS and brake light come on?

Typically, both lights indicate a braking system problem or an ABS fault. Causes can range from a simple parking brake issue or low brake fluid to more serious faults in the hydraulic system or wheel-speed sensors. Drive cautiously and seek a professional diagnostic as soon as possible.

What the lights mean

The ABS (anti-lock braking system) light signals a fault within the ABS, which could prevent wheel lockup control during hard braking. The brake warning light usually indicates a problem with the hydraulic braking system, such as low fluid, a leak, or an issue with the master cylinder or parking brake switch. When both lights appear together, it often points to a broader brake-system issue or a fault in the ABS electronics that affects both systems. Keep in mind that the exact meaning can vary by vehicle, so consult the owner's manual and have a technician diagnose the car with the appropriate tools.

Most frequent causes

Below are the most common reasons both warning lights might illuminate at the same time. Some are easy fixes, while others require professional service.

• Low brake fluid level or a brake fluid leak in the hydraulic system


• Parking brake is engaged, not fully released, or has a faulty switch


• Faulty wheel speed sensor or damaged wiring around the ABS tone rings


• Malfunctioning ABS control module or hydraulic ABS pump



• Master cylinder failure or brake lines with a leak affecting hydraulic pressure

These issues can affect braking performance and ABS function, potentially compromising safety. A professional inspection is warranted if either light is on.

What to do now

If the ABS and brake lights are lit, take these safety-minded steps to assess the situation and prepare for a diagnostic.

1. Safely pull over as soon as possible and check your braking feel. If braking seems normal, you can continue cautiously; if it feels spongy or you notice reduced braking power, stop and tow.


2. Ensure the parking brake is fully released and not sticking.


3. Inspect the brake fluid reservoir. If the level is low, top up with the correct fluid for your vehicle and check for visible leaks. Do not drive long distances with low fluid.


4. Look under the car for signs of fluid leaks around the brake lines, calipers, or the master cylinder.


5. Avoid hard braking or high-speed driving until a professional has diagnosed the issue.

These steps are preliminary safety checks. A proper diagnosis requires a professional scan of the ABS and braking system to retrieve fault codes and inspect components.

What a mechanic will check

During service, a technician will typically perform a thorough diagnostic to identify the root cause and the necessary repairs.

• Connect a professional ABS scanner to read fault codes from the ABS/traction control system


• Inspect wheel speed sensors, wiring, and connectors for corrosion or damage


• Check the ABS pump, valve block, and hydraulic lines for leaks or failure


• Inspect the brake master cylinder and hydraulic fluid for signs of internal leakage


• Assess general brake wear and condition, including pads and rotors


• Verify the brake light switch and related fuses/relays are functioning properly

Timely diagnosis helps restore braking reliability and safety. Depending on the fault, repairs can range from sensor cleaning or replacement to module repair or hydraulic system fixes.

Summary

When ABS and brake lights come on, treat it as a potential safety issue. Start with basic checks and seek professional diagnosis promptly to determine whether the problem is a simple fluid issue or a more complex ABS/hydraulic fault. Never ignore warning lights, and prioritize safe driving or towing to a repair shop.

Is it safe to drive with ABS light on and brake light on?

No, it is not safe to drive with both the ABS and brake lights on; this combination indicates a serious issue with the primary braking system, and you should have your vehicle towed to a mechanic for inspection immediately. Driving with both lights on puts you and others at risk, as it suggests a problem like low brake fluid or a leak that could cause brake failure. 
What to do

• Pull over immediately: Stop your car in a safe location as soon as possible. 
• Do not drive the car: Do not attempt to drive the vehicle to the mechanic yourself. 
• Call for a tow: Arrange for your vehicle to be towed to a professional mechanic for a thorough inspection and repair. 

Why it's dangerous

• Combined failure: The brake light coming on with the ABS light signifies a problem with the entire braking system, not just the anti-lock feature. 
• Risk of brake failure: Issues like low brake fluid or a leak can severely compromise your ability to stop the vehicle effectively. 
• Loss of control: Without a functioning ABS system, you could lose control of your vehicle, especially in an emergency braking situation or on slippery roads, as your wheels are more likely to lock up. 

1:26Driving with an ABS Light On: What You Need to KnowTikTokmerciejauto · 12mo 0:58Can I drive with my ABS light on? #abssystem #warninglights #cars ...YouTubeMercie J Auto Care, llc · 12mo 1:36Driving with ABS Light On: What You Need to KnowTikTokmerciejauto · 2y (function(){
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Can low brake pads cause ABS light to come on?

Yes, low or worn brake pads can cause the ABS light to come on. This is often because as the pads wear down, they require more brake fluid to engage the brakes, which lowers the fluid level in the reservoir. A low brake fluid level can trigger the ABS warning light, and in some cases, very worn pads can also cause the braking sensors to provide incorrect readings that the ABS system interprets as a fault. 
How worn brake pads trigger the ABS light

• Low brake fluid: As brake pads become thin, the caliper pistons have to extend further. This draws more brake fluid from the master cylinder, causing the fluid level to drop. When the fluid level drops below the sensor in the reservoir, the ABS light may turn on. 
• Uneven braking: Very worn brake pads can lead to uneven braking, which the ABS system can detect as a problem, causing it to deactivate and turn on the light. 
• Strain on the system: Severely worn pads reduce braking performance and put extra strain on other components, including the ABS, which can lead to a fault code and illuminate the warning light. 
• Brake wear sensors: Some modern vehicles have brake wear sensors that physically trigger a warning light when the pads are worn down, which is a separate but related issue that can coincide with the ABS light. 

What to do if your ABS light is on

• Do not ignore the light: An illuminated ABS light means there is a problem with the anti-lock braking system. You should have it inspected as soon as possible because driving with a faulty ABS system can be dangerous. 
• Check brake fluid: A quick check of your brake fluid reservoir is a good first step, but don't just top it off. A low level is a symptom of another problem, such as worn pads or a leak, which needs to be addressed. 
• Inspect the brakes: If you or a mechanic can, inspect the brake pads and rotors for signs of excessive wear. 
• Consult a professional: Have your braking system, including the ABS sensors and fluid levels, inspected by a qualified mechanic to diagnose and fix the root cause of the warning light. 

How to fix ABS and brake light on while driving?

These are:

1. Check your brake fluid: low brake fluid can sometimes trigger the ABS light.
2. Perform a system reset: sometimes, the ABS light can be triggered by a temporary issue or an error in the system.
3. Check the ABS fuse: if the ABS fuse is blown, it could cause the ABS light to come on.

What would cause the ABS and brake light to stay on?

Both the ABS and brake lights coming on simultaneously can indicate a serious problem with your braking system. Common causes include low brake fluid, worn brake pads, faulty wheel speed sensors, or a problem with the ABS module itself. It is advised to have your vehicle inspected by a mechanic as soon as possible, as continued driving could be unsafe. 
Potential causes

• Low brake fluid: The most common reason for the brake light to appear is low brake fluid. This can be due to worn pads or a leak. 
• Worn brake pads: When brake pads are excessively worn, it can trigger both lights. 
• Faulty wheel speed sensor: Each wheel has a sensor that the ABS system uses to monitor speed. If one fails, it will turn on the ABS light. 
• ABS module failure: The ABS module is the computer that controls the system. If it malfunctions, both lights can come on. 
• Electrical issues: A blown fuse, damaged wiring, or other electrical problems can cause the ABS system to fail and trigger the lights. 
• Other issues: Problems with wheel bearings, the ABS hydraulic pump, or even a stuck parking brake can also be the cause. 

What to do

• Do not ignore it: Driving with both lights on can be dangerous. The ABS system may not function properly during hard braking, potentially leading to skidding. 
• Check your brake fluid: The simplest check is to open the hood and look at the brake fluid reservoir. If the fluid is below the minimum line, it needs to be topped off or checked for a leak. 
• Check your owner's manual: Your car's owner's manual may provide specific guidance on what to do when these lights come on. 
• Get a professional diagnosis: A mechanic can use a diagnostic tool to read the specific trouble codes stored in the car's computer, which will pinpoint the exact problem. 

This video explains how ABS works and what happens when a wheel speed sensor is faulty: 58s1A Auto: Repair Tips & Secrets Only Mechanics KnowYouTube · Apr 8, 2023