What causes the ABS light to turn on?

Answer 1

The light is on because the ABS has a problem. Unless you know what you are doing, take it to a professional. Another thing to remember about ABS is that it's easy to damage those delicate wheel speed sensors while doing brake work, or to cause metal particles to attach themselves to the magnet. Either is likely to put the system into default, or make it go permanently into anti-lock mode (called "false modulation"), and turn on the warning lamp. On ABS, speed sensors are at the top of the list of failures. As far as the ABS problems are concerned, the first is speed sensors with metallic particles sticking to the sensor nose. This may cause system default, or make it constantly go into anti-lock mode called 'false modulation.' Make sure the air gaps are correct, and the sensors and tone wheels are clean with no iron filings or debris in the vanes, which can give an erratic speed signal, set a code, and put the system in default. Another problem on wheel speed sensors is an internal break in a wire. Be careful doing any wheel work because those sensors are delicate. The second thing is rust where the sensor mounts or in the wheel speed sensor bore, which makes the sensor hard to remove. Another problem is moisture infiltration into speed sensor electrical connectors, which causes intermittents.