Abs Warning Light Does Not Self-Check, Always On, With No DTCS (1999 Models)
WARNING: This page is about a different car, the 1999 Mercury Mystique, 1999 Mercury Cougar, 1999 Ford Contour, 1998 Mercury Mystique, and 1998 Ford Contour. However, it is still accessible from the selected car via links, so may be relevant.
Possible source of problem may be: ABS control module, faulty instrument cluster, or faulty wiring. See SYMPTOM TESTS under DIAGNOSIS & TESTING.