Pulsating brake pedal and ABS light

I have a 1991 Honda Prelude. The ABS light was on so I went and changed the rotor and brake pads on both the front and back brakes. The ABS light is still on and I'm also getting some pulsating/vibrating from the brake pedal.

What can this be?
thanks

If the ABS light is on there is a problem with the ABS system, you should take it to a dealer or shop and get it inspected. While the light is on the system will not engage so you do not have the benefits of ABS until you get it fixed.

It sounds like the slave pump for the break system may be going out. Also, did you check the lines for a leak?