Brake Booster Pressure Sensor Circuit Low
The P0557 code indicates that the brake booster pressure sensor is reporting a voltage lower than the expected range. This sensor monitors vacuum or pressure in the brake booster to assist braking. A low signal can result from a faulty sensor, wiring issues, or a vacuum leak, potentially causing hard brake pedal or increased stopping distance.
01. Most Common Causes
- Faulty brake booster pressure sensor
- Open or shorted sensor wiring/connector
- Vacuum leak in brake booster system
- Failed brake booster
02. Symptoms You Will Notice
- Hard brake pedal (requires more force)
- Increased stopping distance
- Check Engine Light on
- Possible brake assist failure
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify P0557 and check freeze frame data.
Step 2: Inspect the brake booster pressure sensor connector for damage, corrosion, or loose pins.
Step 3: Test sensor voltage with a multimeter (reference signal vs. ground).
Step 4: Check for vacuum leaks in hoses and booster using a vacuum gauge.
Step 5: If wiring and vacuum are OK, replace the brake booster pressure sensor.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The brake booster may not provide full assist, leading to a hard pedal and longer stopping distances, increasing accident risk.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor, depending on sensor cost and accessibility.