When both your ABS light and brake warning light come on at the same time, it's easy to panic. Your anti-lock braking system and your standard brakes are both telling you something is wrong and ignoring those dashboard warnings can put you and others at risk. Understanding the common causes of ABS and brake light staying on together helps you figure out whether it's a quick fix or something that needs a mechanic right away. This guide walks you through the real reasons these lights trigger simultaneously, how to diagnose the problem, and what to actually do about it.

What Does It Mean When Both the ABS Light and Brake Light Come On Together?

The ABS light and the brake warning light serve different purposes. The ABS light indicates a problem with your anti-lock braking system the system that prevents your wheels from locking up during hard stops. The brake warning light usually signals an issue with your conventional hydraulic braking system, low brake fluid, or the parking brake being engaged.

When both lights are on at the same time, it often points to a shared component or a failure serious enough to affect both systems. In many vehicles, the ABS module, wheel speed sensors, or the brake fluid level sensor can trigger both lights simultaneously. It's your car's way of saying the problem goes beyond one isolated system.

Why You Shouldn't Ignore Both Warning Lights On Together

Driving with both lights on means you may have compromised braking ability. Your standard brakes might still work, but without ABS, your wheels can lock up in emergency stops especially on wet or icy roads. In some cases, the vehicle may go into a fail-safe mode that limits braking performance. Getting to the root cause quickly matters for your safety and can also prevent more expensive repairs down the road.

What Are the Most Common Causes of ABS and Brake Light Staying On Together?

1. Low Brake Fluid Level

This is one of the simplest and most frequent causes. When brake fluid drops below a certain level, the fluid reservoir sensor triggers the brake warning light. In many vehicles, this same condition disables the ABS system, turning on the ABS light as well. Low fluid could mean your brake pads are worn down, or you may have a leak somewhere in the brake lines.

Check the brake fluid reservoir under the hood. If it's below the minimum line, top it off with the correct DOT specification fluid for your vehicle. But don't just top it off and forget about it find out why it was low in the first place.

2. Failed or Dirty Wheel Speed Sensors

Your ABS relies on wheel speed sensors at each wheel to monitor rotational speed. If one or more sensors fail, get coated in brake dust and road grime, or the wiring gets damaged, the ABS module loses its data and triggers the ABS light. Some vehicles will also activate the brake warning light when the system detects a critical sensor failure.

This is especially common after driving through mud, deep water, or after winter road salt exposure. A visual inspection of the sensor and its wiring harness at each wheel is a good starting point.

3. ABS Module or Hydraulic Pump Failure

The ABS control module is the brain of the anti-lock system. When it fails internally often due to corroded solder joints or electrical faults both lights will stay on permanently. The hydraulic pump that modulates brake pressure can also fail, which affects both the ABS function and, in some designs, the overall brake pressure distribution.

ABS module failure is one of the more expensive fixes, but in some cases, the module can be tested at home before committing to a replacement. Many owners have found that a rebuilt or repaired module works just as well as a new one at a fraction of the dealer price.

4. Worn Brake Pads or Rotors

Severely worn brake pads can cause the brake fluid level to drop as the caliper pistons extend further. This triggers the fluid level sensor and, depending on the vehicle, can set off both warning lights. Some vehicles also have electronic wear sensors built into the brake pads that communicate with both the ABS and brake systems.

5. Bad Brake Light Switch

The brake light switch, located near the brake pedal, tells the vehicle's computer when you're pressing the brakes. A faulty switch can send incorrect signals to both the ABS module and the instrument cluster, causing both lights to illuminate. This is a relatively inexpensive part and a common fix on many makes and models.

6. Wiring and Connector Issues

Corroded, damaged, or loose wiring and connectors between the ABS module, wheel speed sensors, and the vehicle's main computer can cause intermittent or permanent warning light issues. This is especially common in older vehicles or those driven in harsh climates with road salt and moisture exposure.

7. Failing ABS Relay or Fuse

The ABS system has its own relay and fuse. If either one fails, the system loses power, and the ABS light turns on. Depending on how the vehicle's computer is programmed, it may also illuminate the brake warning light as a secondary alert.

How Do I Figure Out Which Cause Is the Problem?

Start with the basics. Check your brake fluid level. Look at your brake pads. Make sure the parking brake is fully released. If those check out, the next step is scanning for diagnostic trouble codes (DTCs) with an OBD-II scanner that can read ABS codes a standard code reader often won't pull ABS-specific codes.

Common ABS-related codes include:

• C0035–C0051 Wheel speed sensor circuit issues
• C0110 ABS pump motor circuit fault
• C0161 Brake switch circuit malfunction
• C0550 ECU/ECM internal failure

Once you have a code, you can narrow down the diagnosis significantly. If you're seeing module-related codes, it's worth looking into specific symptoms of ABS module failure to confirm whether that's your issue before buying parts.

Can I Drive With Both the ABS and Brake Light On?

You can drive, but you should do so cautiously and get the issue fixed as soon as possible. Your base hydraulic brakes will usually still function, but you've lost ABS protection. In an emergency stop, your wheels may lock up, and you'll lose steering control during hard braking. On wet or gravel roads, this can be genuinely dangerous.

If the brake pedal feels soft, spongy, or sinks to the floor stop driving immediately and have the vehicle towed. That signals a hydraulic failure, not just an electronic warning.

Common Mistakes People Make With This Problem

1. Just clearing the codes and hoping it goes away. The lights will come back. The underlying problem is still there.
2. Replacing the ABS module without proper diagnosis. The module is expensive. Make sure it's actually the problem first. A wheel speed sensor or a bad ground wire can look like a module failure on a scan tool.
3. Topping off brake fluid without checking for leaks. If the fluid was low, something caused it. Leaking brake lines or a failing master cylinder need attention.
4. Ignoring intermittent warnings. If the lights flicker on and off, the problem is developing. Catching it early usually means a cheaper fix.
5. Using a basic OBD-II scanner that doesn't read ABS codes. You'll get engine codes but miss the real issue. You need a scanner with ABS capability to get the full picture.

How Much Does It Cost to Fix?

Costs vary widely depending on the cause:

• Brake fluid top-off: Under $20 for fluid, but investigate the cause
• Wheel speed sensor replacement: $100–$300 per sensor (parts and labor)
• Brake light switch: $50–$150
• Brake pads and rotors: $150–$500 per axle
• ABS module replacement: $500–$1,500+ at a shop; significantly less with a DIY approach or a rebuilt module

Practical Next-Step Checklist

• Check brake fluid level top off if low, and look for leaks
• Inspect brake pads replace if worn past the minimum thickness
• Make sure the parking brake is fully released
• Scan for ABS codes with a scanner that supports ABS (not just engine codes)
• Inspect wheel speed sensors and wiring at all four wheels for damage or buildup
• Check the brake light switch near the brake pedal for proper operation
• Test the ABS module if codes point to an internal fault before buying a replacement
• Clear the codes after the repair and drive to confirm the lights stay off

For more detail on walking through this process yourself, see this step-by-step diagnosis guide that covers what to check in order and how to handle ABS module repairs at home. You can also reference this NHTSA resource on anti-lock braking systems for a general safety overview.