Which factor can lead to brake pulsation during operation?

Brake pulsation during operation is primarily caused by warped rotors. When the brake rotors are warped, they do not have a consistent surface for the brake pads to grip. As the brake pads make contact with the warped surface, the uneven wear results in variations in the brake force applied, which can create a pulsating sensation in the brake pedal. This condition is typically felt more intensely during braking due to the constant friction and heat generated, which can further exacerbate the problem.

The other factors listed do not directly lead to brake pulsation. Low tire pressure can affect vehicle handling and tire wear but does not cause pulsation in the braking system itself. A faulty alternator and an overcharged battery pertain to the electrical system of the vehicle and have no effect on the mechanical operation of the braking system. Therefore, the only factor among the choices that leads to brake pulsation is warped rotors.