ABS warning light: what it means and can you drive?

ABS stands for anti-lock braking system. When you brake hard, it stops the wheels from locking up, so you can still steer while the car slows down. The ABS light is usually amber and shows the letters "ABS" in a circle, but symbols vary between makes, so check your owner's manual.

Like most warning lights, it comes on for a moment when you switch on the ignition and should then go out. If it stays on, or comes on while you drive, the system has found a fault and has probably switched itself off.

What still works: your normal brakes. The RAC and the AA both say it is generally fine to continue your journey carefully. What may not work: the anti-lock function, and on many cars the traction and stability control, which use the same sensors. In a sudden stop, especially on a wet or icy road, the wheels can lock and the car can take longer to stop.

When to stop: if the red brake warning light is on as well, or the pedal feels soft, goes down further than normal, or you hear noises from the wheels. The RAC says the ABS light together with the brake warning light could mean the brake system is failing, and you should stop straight away. See our brake warning light guide.

Likely causes, most common first

1. Faulty wheel speed sensor

   Each wheel has a small sensor that reports how fast it is turning. If one sensor fails, gets caked in dirt or brake dust, or is damaged, the ABS can no longer compare the wheels and switches itself off. This is the cause in most cases.

2. Damaged or corroded sensor wiring

   The sensor wires run close to the wheels, where they get wet, salted and knocked about. A chafed or corroded wire or connector cuts the signal just like a dead sensor.

3. Low brake fluid

   Low fluid can trigger the ABS light, often together with the red brake warning light. Low fluid can mean a leak or very worn pads, so do not just top it up and forget it.

   Read the fix guide →

4. Damaged sensor ring or worn wheel bearing

   The sensor reads a toothed ring on the hub or driveshaft. If the ring is cracked or rusty, or a worn wheel bearing lets the hub move, the readings become unreliable.

5. Blown fuse or ABS control unit fault

   Less common. A blown fuse can switch the system off. The ABS pump and control unit can also fail, which is the most expensive repair.

What it costs to fix

The first step is a diagnostic check, where a garage reads the fault code from the ABS control unit. That code usually points to the wheel or part that needs attention.

DIY or garage?

How to prevent it

• Rinse road salt and mud from the wheel arches in winter.
• Have the brake fluid level and condition checked at each service.
• Ask the garage to look at the sensor wiring when they work on the brakes or wheel bearings.
• If the light comes on, get it checked soon. In the UK it is an MOT failure.