P0555
UniversalBrake Booster Pressure Sensor Circuit Malfunction
High SeverityThis code indicates an electrical problem within the Brake Booster Pressure Sensor circuit, which monitors the vacuum level in the brake booster. A malfunction here can lead to reduced power assist for braking, making the brake pedal feel harder to press and potentially increasing stopping distances.
⚠️ Before You Begin (Safety First)
Always prioritize safety when working on your vehicle's braking system. Before performing any work, disconnect the battery's negative terminal to prevent accidental airbag deployment or electrical shorts. Ensure the vehicle is securely supported on jack stands if working underneath. If you are unsure about any step, consult a professional mechanic. Improper brake repairs can lead to serious accidents.
Common Symptoms
- Check Engine Light illuminated
- Hard brake pedal
- Reduced brake power assist
- Increased stopping distance
Common Causes
- Faulty Brake Booster Pressure Sensor
- Damaged, corroded, or open wiring in the sensor circuit
- Shorted wiring in the sensor circuit
- Loose electrical connections at the sensor or PCM
- Less commonly, a faulty Powertrain Control Module (PCM)
Frequently reported on: General/Universal
Diagnostic Steps
- Safely park the vehicle on a level surface and engage the parking brake. Disconnect the negative battery terminal.
- Locate the brake booster pressure sensor. It is typically mounted on the brake booster, which is the large, round component located between the brake master cylinder and the firewall.
- Visually inspect the sensor's electrical connector and wiring for any signs of damage, corrosion, fraying, or loose connections. Repair or replace any damaged wiring.
- If wiring appears good, use a multimeter to test for proper voltage supply to the sensor and continuity in the circuit. Refer to your vehicle's specific wiring diagrams for correct voltage specifications and pinouts.
- If voltage and ground are present, and the wiring is intact, the sensor itself may be faulty and require replacement. Follow manufacturer's instructions for removal and installation.
- Reconnect the battery, clear the P0555 code using an OBD-II scanner, and test drive the vehicle to ensure the symptoms are gone and the code does not return.
👨🔧 When to Call a Professional
If you experience a consistently firm brake pedal, increased stopping distances, or if you are not comfortable performing electrical diagnostics, it is crucial to have a professional diagnose and repair the issue immediately. This affects your vehicle's fundamental safety system.
Commonly Asked Questions
What does the Brake Booster Pressure Sensor do?
The Brake Booster Pressure Sensor monitors the vacuum level inside the brake booster, which provides power assistance for braking. This information is used by the engine control unit to ensure proper brake function.
Is it safe to drive with a P0555 code?
Driving with a P0555 code is not recommended, especially if you notice a harder brake pedal or reduced braking performance. This issue directly affects a critical safety system, and driving could lead to increased stopping distances or an inability to stop effectively.
What are the most common causes of P0555?
The most common causes include faulty wiring (corroded, open, or shorted circuits) leading to the sensor, a defective brake booster pressure sensor itself, or sometimes a poor electrical connection.
How can I test the Brake Booster Pressure Sensor?
You can test the sensor by checking the voltage supply, ground, and signal output using a multimeter while referring to your vehicle's specific service manual or wiring diagram. Some advanced OBD-II scanners can also show live data from the sensor.
Is this code related to a vacuum leak?
While a vacuum leak affecting the brake booster could indirectly cause the sensor to report incorrect readings, the P0555 specifically indicates an electrical circuit malfunction of the sensor itself, rather than a mechanical vacuum issue with the booster. However, a significant vacuum leak could potentially impact the sensor's signal.