Which incorrect service procedure could lead to brake pedal pulsation?

Brake pedal pulsation is often caused by issues related to the braking system's components and their alignment. When the brake rotors are machined on a lathe, it is crucial that they are properly set up to ensure an even surface. Incorrect run-out, which refers to the amount of deviation from true circularity in the rotor, can lead to uneven contact between the brake pads and rotors during braking.

If the rotor is not parallel and has incorrect run-out, it causes the brake caliper to exert inconsistent pressure on the brake pads as the wheel spins. This inconsistency creates vibrations felt through the brake pedal, resulting in the pulsation effect. Therefore, incorrect run-out on the brake lathe is directly linked to brake performance and can lead to the undesirable pulsation of the brake pedal when engaged.

In contrast, improper brake fluid level, worn brake linings, and replaced brake light bulbs do not directly contribute to brake pedal pulsation. While low brake fluid could potentially cause braking issues, it doesn't specifically relate to the pulsation symptom, and worn brake linings mainly affect stopping power and braking efficiency without causing a pulsation sensation. Replaced brake light bulbs have no relevance to the braking performance or feel of the pedal, further separating them