P0557
Brake Booster Pressure Sensor Circuit Low
Brakes / booster pressure sensor
Generic OBD-II
High
What it means
P0557 means the brake booster pressure (vacuum) sensor is reporting an abnormally low voltage — its signal has dropped below the normal range, usually from a short to ground or an open in the circuit. The engine still starts and runs, but the system that manages brake-boost assist may not have an accurate pressure reading.
High
Can I keep driving? Have it checked promptly — on vehicles that use this sensor to manage brake assist, a fault can reduce or change power-brake feel; the engine still starts and runs normally.
Common symptoms
What you'll notice
- Check-engine light on
- Reduced or inconsistent power-brake assist (firmer pedal) on vehicles that use this sensor
- A brake warning message or light on some vehicles
- Cruise control or driver-assist braking features disabled on some vehicles
Common causes
Most likely first
- Short to ground or an open in the sensor's signal or ground wiringLikely
- Corroded or loose connector at the brake booster pressure sensorCommon
- Failed brake booster pressure sensorCommon
- Loss of the sensor's supply voltage from the module (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and scan for related brake or booster codes.
- Inspect the sensor connector and wiring for corrosion, shorts to ground, and opens.
- With the key on, back-probe the sensor's signal and reference voltages against spec.
- Replace the brake booster pressure sensor if the wiring and supply voltage check good.
- Clear the code and road-test to confirm the fix.
FAQ
Quick answers
Is it safe to drive with P0557?+
Because it touches the brake-assist system, get it diagnosed soon. The brakes still work mechanically, but assist may be reduced on some models.
Can I just clear P0557?+
It returns until the shorted or open circuit — or the sensor itself — is repaired.
Related codes
Often seen with P0557
Read & clear P0557 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX