Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
There are many areas of the ABS/TCS system that will cause the light to come on when there is a malfunction in them. The first thing you would want to do is to have it scanned for trouble codes, (current and history) to see where the problem may be.
There has been a service bulletin for the front wire harness on them, you will want to check them as well, if the code(s) points to the front wheel speed sensor area.
Bulletin No.: 03-05-25-008
Date: October 01, 2003
Intermittent/Constant ABS MIL Illuminated (Replace Both Front Wheel Speed Harnesses)
Some customers may comment on an intermittent or constant ABS malfunction indicator light.
The front wheel speed sensor harness may wear or come into contact with the tie rod end stud. Additionally, the harness may, in some instances, loop over the tie rod stud. In this case, the wheel speed sensor should be examined for damage.
Replace original wheel speed sensor harnesses by splicing in revised wheel speed sensor harnesses. The new design harnesses are of a different length and have revised retention clip locations.