Brake Booster Pressure Sensor Circuit Malfunction
The P0555 code indicates a problem in the brake booster pressure sensor circuit. This sensor monitors vacuum or pressure in the brake booster to assist braking. A fault can cause the powertrain control module (PCM) to detect an abnormal signal, often due to electrical issues, sensor failure, or vacuum leaks. This can lead to hard brake pedal or increased stopping distance.
1. Most Common Causes
- Faulty brake booster pressure sensor
- Open or shorted wiring in sensor circuit
- Poor electrical connection at sensor
- Vacuum leak in brake booster system
- Failed PCM (rare)
2. Symptoms You Will Notice
- Illuminated Check Engine Light
- Hard brake pedal (increased effort)
- Reduced braking performance
- Possible ABS or traction control warning
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect wiring and connector at brake booster pressure sensor for damage or corrosion.
Step 3: Test sensor voltage and ground with a multimeter; compare to manufacturer specs.
Step 4: Check for vacuum leaks in hoses to brake booster.
Step 5: Replace sensor if circuit tests OK but sensor fails output test.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. The brake booster may not assist properly, requiring more pedal force and increasing stopping distance, which can be dangerous.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor, but can be higher if wiring repairs or PCM replacement is needed.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.