There are several reasons why an ABS light may stay on, including an issue with the traction control system, a defective sensor or the main computer. In order to diagnose this, with the light on, run a diagnostics scan.
When the ABS light comes on and stays on, this could be a sign that the traction system is disabled, which could mean that if you were to stop suddenly, your wheels would lock up and slide; it would also affect how well the vehicle drives in wet conditions.
Major problems exist if the issue is because of the main computer in the vehicle. A malfunction in the computer will affect how the vehicle drives. For safety reasons, it is imperative that this issue be checked as soon as possible.