Brake Booster Pressure Sensor

The power brake booster pressure sensor informs the ECM of brake booster vacuum pressure. It is located inline to or fitted into the brake booster with a snug rubber grommet. The control module will set a code (P0555) and illuminate the check engine or brake warning light when a fault is found in the sensor or its circuit.

A faulty sensor will result in erratic braking and a spongy/hard brake pedal. The sensor converts vacuum pressure in the power brake booster to a voltage signal for the ECM. An inaccurate signal from the sensor will affect brake and engine performance. The vehicle may have symptoms of a bad brake booster or check valve/hose resulting in a hard brake pedal with longer than average stopping distances.

Rubber grommets can harden in the engine compartment. A hardened cracked and leaking grommet, a vacuum leak, or a clogged or cracked hose will affect the sensor's operation. The brake booster pressure sensor is located in the engine compartment close to the master cylinder. It’s important to inspect the wiring and connections for looseness and wear before replacing the sensor.