ABS light stays on

You don't mention what was replaced, but it is possible that whatever was replaced was not the cause of the problem, or more likely that your ABS controller unit itself has failed, and needs to be replaced.

Thanks for replying so promptly, littlehorn. As far as parts replaced, the list is as follows rear wheel cylinders and brake shoes, the drums were turned. I also replaced the front rotor and caliper on the right side, and the master cyliner and power brake booster. The power brake booster was making a hissing sound and needed replacing. I bled the brake lines at the wheels and at the master cylinder as well as at the ABS controller. Is there any way to test the ABS unit? Do I have to take it in to have it diagnosed?