Brake Booster Pressure Sensor Circuit Range/Performance
The P0556 code indicates that the Engine Control Module (ECM) has detected a signal from the brake booster pressure sensor that is outside the expected range or performance parameters. This sensor monitors vacuum or pressure in the brake booster to assist with braking. A fault can affect brake assist and may lead to a hard brake pedal or increased stopping distance.
01. Most Common Causes
- Faulty brake booster pressure sensor
- Wiring or connector issues in the sensor circuit
- Vacuum leak in the brake booster system
- Faulty ECM (rare)
02. Symptoms You Will Notice
- Hard brake pedal requiring more effort
- Increased stopping distance
- Illuminated Check Engine Light
- Possible ABS or traction control warning lights
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm P0556 and check for other codes.
Step 2: Inspect the brake booster pressure sensor connector and wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor's voltage signal with a multimeter; compare to manufacturer specifications.
Step 4: Check for vacuum leaks in the brake booster hose and connections.
Step 5: If sensor and wiring are okay, replace the brake booster pressure sensor.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. The brake booster may not provide full assist, leading to a hard brake pedal and increased stopping distance, which can be dangerous.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor, depending on the vehicle and shop rates. The sensor itself is often inexpensive.