The Anti Lock light is coming on intermittently on my '98 Disco I. It clears the startup and turns off after 3 mph. Typically it will stay off unless the roads are wet/snowy and then it will come on after 10-15 miles of driving and stay on until the car is turned off and restarted. If the roads are dry, it normally doesn't come on at all. Any suggestions of where to look first for problems? The brakes work as they should when the light is on. Thanks!