Pump should come on every few times, brake pedal pressed.
If vibration felt when stationary (not driving). Could be bearings in pump or it's motor.
If vibration in pedal, is while driving. This if called brake pedal pulse. It's due to brake rotor disk, run-out exceeding limit. The hotter the brake (actively use), the more you'll feel.
I'm having issue with run-out! Typically I do not put a run out gauge on turned Rotors or new OEM. But decided to in this case, on just one to start with. Well ended up put run-out dial gauge on all. Procedure is to remove rotor and turn to new position on hub, if out of spec, or just wanting...
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