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Most dashboard warnings can wait until the weekend. These two cannot always, and the trouble is that they look similar enough that people treat them the same way. They are not the same. One tells you a driver-assistance system has switched off. The other can be telling you that your ability to stop the car is compromised right now.
This guide separates them clearly, tells you what causes each, and gives you a straight answer on when to keep driving and when to stop.
The two lights at a glance
- Red BRAKE light — usually the word BRAKE, or an exclamation mark inside a circle within parentheses. Red is the colour manufacturers reserve for “this may be a safety problem”. It relates to the base hydraulic braking system: fluid level, hydraulic pressure, or the parking brake.
- Amber ABS light — the letters ABS, usually inside a circle within parentheses. Amber means a system has faulted and switched itself off. Your ordinary brakes still work; what you have lost is anti-lock function during hard braking.
The short version: amber ABS on its own is a “get it looked at” problem. Red BRAKE is a “check it now” problem. Both together is a “stop driving” problem.
Red brake warning light: what causes it
1. The parking brake is engaged
Always check this first. A partially released lever or an electronic parking brake that has not fully disengaged will light it up. Release it fully and see if the light clears. Driving with the parking brake partly on will cook the rear brakes.
2. Low brake fluid
The most common genuine cause. There is a level sensor in the master cylinder reservoir, and it has two very different meanings:
- Worn brake pads. As friction material wears away, the caliper pistons extend further to reach the disc, and the extra fluid needed to fill that space comes out of the reservoir. The level dropping slowly over tens of thousands of miles is a normal consequence of pad wear. Check your pad thickness — our brake pad intervals and warning signs guide covers what to look for.
- A leak. A sudden drop is a different matter entirely. Brake fluid is a sealed hydraulic system; it does not evaporate. If the level fell quickly, it went somewhere — a corroded brake line, a leaking caliper seal, a failed wheel cylinder, or the master cylinder itself.
3. Loss of hydraulic pressure
Modern systems are split into two circuits so that one failure does not remove all braking. A pressure differential switch detects when the two circuits are no longer balanced and lights the red warning. This is the serious version, and it usually comes with a pedal that feels wrong.
4. A faulty level sensor
Sensors fail, and sometimes the light is on with perfectly adequate fluid. Verify the actual level by eye against the reservoir markings before assuming the sensor lied to you.
Amber ABS light: what causes it
- A failed wheel speed sensor. By far the most common cause. These sit at each hub in road spray, salt and brake dust.
- A damaged or contaminated tone ring. The toothed ring the sensor reads can rust, crack, or pack with debris, producing an erratic signal.
- Wiring damage. The harness to each wheel flexes constantly with suspension and steering movement, and eventually chafes.
- A blown fuse or relay. Cheap, quick to check, and easy to overlook.
- Low system voltage. A weak battery or failing alternator sets ABS faults readily. Test the battery before buying sensors — our battery testing guide explains how.
- The ABS module or pump itself. Less common, considerably more expensive.
Because ABS shares its wheel speed sensors with stability control, an ABS fault very often lights the traction control warning at the same time. Our traction control light guide covers that overlap in detail.
Both lights on together: treat this as serious
When the red brake light and the amber ABS light illuminate simultaneously, it commonly indicates that electronic brakeforce distribution has been disabled.
That system continuously balances braking between the front and rear axles based on load and weight transfer. Without it, a hard stop can put too much braking force on the rear wheels, which can lock them and cause the back of the car to step out — precisely the situation you cannot easily recover from.
The car may feel entirely normal in gentle driving, which is exactly what makes this dangerous. The failure only reveals itself in an emergency stop. Do not drive on this combination.
When to stop driving immediately
Pull over as soon as it is safe and arrange recovery if any of these apply:
- The brake pedal feels soft, spongy, or sinks slowly toward the floor under steady pressure
- You have to pump the pedal to get a firm response
- The red brake light and the ABS light are on together
- The red brake light came on suddenly along with a noticeable change in braking feel
- You can see fluid on the inside of a wheel, on a brake line, or pooled under the car — brake fluid is typically clear to light amber and slightly oily
- The car pulls sharply to one side when braking
- You hear grinding metal-on-metal when braking
An amber ABS light on its own, with a firm pedal and normal braking feel, does not require this. Drive gently, leave extra following distance, avoid hard stops, and get it diagnosed soon.
Tools and materials you’ll need
- A scan tool capable of reading ABS and chassis codes, not just engine codes — see our scanner comparison
- A flashlight
- Jack and jack stands, or ramps — never work under a car supported only by a jack
- Correct-specification brake fluid for your vehicle, unopened
- A multimeter
- Basic hand tools and a wire brush
Step-by-step diagnosis
- Test the pedal before anything else. With the engine running and the car stationary, press the brake pedal and hold steady firm pressure for about thirty seconds. It should stay put. If it slowly sinks, you have an internal leak, most likely in the master cylinder. Stop here and call for recovery.
- Confirm the parking brake is fully released. Cycle it on and off.
- Check the brake fluid level. Look at the reservoir under the hood and compare against the minimum and maximum marks. Note the colour too — fresh fluid is clear to light amber, while very dark fluid indicates moisture and age and is due for replacement.
- If fluid is low, find out why before topping up. Inspect each wheel for wetness on the inside of the tire or on the caliper, and follow the hard lines along the underbody looking for corrosion or damp patches. Then check pad thickness. Topping up fluid to silence the light while a leak drains it is genuinely dangerous.
- Scan for ABS codes. Chassis codes normally name the specific wheel, which turns a broad problem into a narrow one.
- Inspect the indicated wheel speed sensor. Look for a corroded connector, a chafed wire, or a tone ring packed with rust and debris. Cleaning the tone ring resolves a fair share of these.
- Check the battery and charging voltage if codes are scattered across several modules with no obvious pattern.
- Check the fuses for the ABS system before condemning the module.
Common mistakes
- Topping up brake fluid without investigating. This is the mistake that turns a leaking line into brake failure.
- Ignoring an ABS light because the brakes “feel fine”. They will feel fine right up until the moment you need to stop hard on a wet road.
- Using the wrong brake fluid. Specifications are not interchangeable. Use exactly what the reservoir cap or manual specifies, and never use fluid from a container that has been open, since brake fluid absorbs moisture from the air.
- Assuming the red light always means low fluid. It also covers hydraulic pressure loss, which is far more urgent.
- Replacing an ABS sensor without checking its wiring first. The wire fails more often than the sensor.
- Driving on both lights. Covered above, and worth repeating.
Frequently asked questions
Can I drive with just the ABS light on?
Yes, with care. Your normal hydraulic brakes are unaffected. What you lose is anti-lock function, meaning the wheels can lock under heavy braking and you lose steering control while they are locked. Drive conservatively, allow more distance, and get it fixed promptly.
Why does my ABS light come on only sometimes?
Intermittent faults usually point to wiring: a chafed wire that only breaks contact over bumps, or a connector that loses continuity when wet. They can also come from a marginal wheel speed sensor that fails only when hot.
Is the brake light related to my brake lamps at the back?
No, though the confusion is understandable. The dashboard brake warning concerns the braking system. A separate bulb-out warning covers the exterior lamps, and a failed brake light switch can cause its own unrelated set of problems.
How often should brake fluid be replaced?
Brake fluid is hygroscopic, meaning it absorbs moisture from the atmosphere over time, which lowers its boiling point and corrodes internal components. Most manufacturers specify replacement every two to three years regardless of mileage. Check your manual for the interval that applies to your car.
When to call a professional
Braking is the one system where the cost of getting it wrong is not measured in money. Hand it over if:
- The pedal is soft, sinking, or requires pumping
- Both warning lights are on
- You have found a fluid leak anywhere in the system
- The work involves opening the hydraulic system, which requires correct bleeding to remove air
- Codes point to the ABS module or pump assembly
- Brake lines show corrosion — these need replacing, not patching
- You are not fully confident in the repair. There is no acceptable margin for error here