how to fix my abs warning light on 1999 ford galaxy?

DIY depends on how good you are and what the fault is!!
Repair by trial and error is pointless and expensive.
If you have, and can use, a multi-meter and/or oscilloscope you can test each corner for failure, but that wont be much help if it's a pump problem.

Check all the fuses, have a look at the wheel sensors and their plugs to make sure there's nothing obviously wrong. Check the multiplug on the ABS pump.
If there is nothing obvious you'll have to take it to a garage with the appropriate diagnostic equipment and have the fault codes checked.
Put up the results in a new post and we can discuss options.
Some garages will refund the cost of the diag test if they are given the repair job, bear that in mind when costing.

artie
June 2009