What does an illuminated ABS warning light mean?
The warning light normally lights up briefly after the ignition is switched on during a self-check of the system. If it does not go out after starting or comes on while driving, the control unit has detected a fault. The anti-lock function may then not be available, so the wheels may lock during hard braking. Always check the exact meaning of the warning in the manual of the specific car.
Is it possible to continue driving with the light on?
If only the yellow ABS light is on, the brake pedal behaves normally, and the red brake warning light is off, the basic braking system usually remains functional without ABS support. Drive carefully, increase your distance, avoid hard braking and have the car inspected as soon as possible. In wet, snowy or slippery surfaces, limiting the system is especially important.
When to safely stop and stop driving
Stop driving if the red brake light comes on at the same time, the pedal is soft or drops, the car drags significantly when braking, the braking effect has weakened or brake fluid is leaking. In such a situation, stop safely and choose tow. Follow the same procedure whenever you are unsure of the condition of the brakes; the instructions in the vehicle manual are decisive.
Where can be the cause
A common fault circuit is the speed sensor of a wheel, its wiring or connector. The problem may also be related to the sensor ring, wheel bearing, system power supply, hydraulic unit or ABS control unit. The same warning light can therefore be triggered by different faults, and the error code itself may not yet confirm a faulty part.
Why can ESP or traction control also light up?
ABS also uses wheel rotation data for other stabilization and traction functions. When there is no reliable signal from a wheel or there is another fault in the system, together with ABS, ESP, ESC or traction control can also light up. In some cars, other assistance functions may also be temporarily limited; the specific range depends on the construction of the car.
How does ABS diagnostics work?
First, the fault memory of the ABS control unit is read and the live data from the wheel sensors is compared. This is followed by a check of the wiring, connectors, power and mechanical parts of the bike; depending on the result, also targeted electrical measurement. After the repair, the defect is erased, the return of signals and the function of the system are verified during a safe test drive.
Every vehicle and fault is different. This article provides general guidance; an inspection of the specific vehicle determines the correct procedure.