The ABS light means the anti-lock braking system has detected a fault and has most likely switched itself off. Your normal brakes keep working, but the wheels can lock up during emergency braking. ESP/traction control often switches off at the same time.
When to stop immediately
If the red brake warning (BRAKE or "!" in a circle) is on together with the ABS light, there may be a problem with the brake fluid level or brake force distribution. Check the brake fluid level straight away and don't drive if the pedal feels soft.
Most common causes
- Wheel speed sensor: by far the most common cause. The sensor or its wiring gets damaged, especially at the front wheels.
- A dirty or rusty sensor ring (reluctor/tone ring) – common on older cars where the ring sits on the driveshaft or hub.
- Wheel bearing: on many cars the magnetic sensor ring is built into the bearing. A worn bearing gives a false signal.
- A blown fuse, a loose connector or low battery voltage.
- Less often, the ABS module or pump itself (for example cracked solder joints in the control unit).
What you can check yourself
- The brake fluid level.
- Did the light come on after a tyre change or other work? A sensor wire may have been damaged or a connector left unplugged.
- Does the light appear only at certain speeds or on bumpy roads? That points to a broken wire or bearing play.
Diagnosis
ABS fault codes are not part of the generic engine OBD2 codes – you need a reader that can talk to the ABS module. With a diagnostic tool we can watch all four wheel speeds while driving and see which sensor gives a wrong reading.
Driving with the ABS light on
Short careful trips are usually possible, but keep larger distances, brake earlier and avoid emergencies on wet or icy roads. In Estonia an active ABS warning is also a reason to fail the technical inspection.
Describe your symptoms in Diagno's AI diagnosis. A trusted mechanic with an ABS-capable scan tool can read the module codes and test the sensors.