ABS light on with pulsing brake pedal

This should be pretty easy for your mechanic to identify. The typical causes are a bent wheel, bent hub, warped brake rotor, rust or other debris stuck between the wheel and rotor or the rotor and hub, and a broken belt in one of the tires. In severe cases it can be caused by not using a click-type torque wrench on the lug nuts.

Start by running the car in gear with the wheels off the ground. Watch the tread for signs of squirming from side to side or a bulge hopping up and down. Next, watch the edge of the wheel where the balancing weights go. That should not be moving side-to-side as the wheel goes around.

Was the alignment checked after the parts were replaced?