P0557 indicates that the Engine Control Module has detected a low voltage condition in the brake booster pressure sensor circuit, meaning the sensor signal is below the expected minimum range.
The sensor itself has failed or is providing an abnormally low voltage signal.
Damage, corrosion, or a broken wire in the sensor circuit can cause a low voltage reading.
A high‑resistance or missing ground at the sensor or connector can pull the signal down.
Vibration or moisture can cause the connector pins to lose contact or become corroded.
A malfunction inside the control module’s input circuit is possible but is the least likely cause.
No. In real‑world experience the PCM is rarely the cause; replacing it is usually unnecessary and expensive. Diagnose the sensor and wiring first.
The light will turn off only if the underlying fault is resolved. If the sensor or circuit still reads low, the code will return and the light will illuminate again.
The vehicle will have reduced brake assist, which can affect stopping distance. It is advisable to have the problem corrected before normal driving, especially in heavy traffic or adverse conditions.
Yes. The brake booster pressure sensor data is used by ABS, ESC, and stability control. A fault can cause these systems to disable or operate in a limited mode.