Brake Booster Pressure Sensor Circuit
The P0555 code indicates a malfunction in the brake booster pressure sensor circuit, which monitors vacuum pressure in the brake booster system. This sensor helps the engine control module ensure proper brake assist function, and a circuit fault can reduce braking efficiency or trigger warning lights.
What You Might Notice
- Check Engine Light or Service Engine Soon Light illuminated
- Check Brake Light flashing or staying on during braking
- Increased brake pedal effort required to stop the vehicle
- Reduced brake booster assist feeling soft or spongy brakes
- Vehicle may go into limp mode with reduced performance
Most Common Causes
- 1
Defective brake booster pressure sensor
The sensor itself fails electrically or mechanically, sending incorrect or no signal to the PCM. This is the most common cause of P0555.
- 2
Worn or damaged vacuum lines
Cracks, splits, or loose connections in vacuum hoses reduce pressure signal accuracy to the sensor. Vacuum leaks prevent proper sensor readings.
- 3
Corroded or damaged connector
The sensor connector develops corrosion, loose pins, or water intrusion that breaks the electrical circuit. This prevents proper signal transmission.
- 4
Damaged wiring or faulty PCM
Wiring harness damage, breaks, or short circuits in the sensor circuit can cause signal loss. In rare cases, PCM programming errors or failure cause the code.
How to Diagnose It
- 1
Check Defective brake booster pressure sensor — The sensor itself fails electrically or mechanically, sending incorrect or no signal to the PCM. This is the most common cause of P0555.
- 2
Check Worn or damaged vacuum lines — Cracks, splits, or loose connections in vacuum hoses reduce pressure signal accuracy to the sensor. Vacuum leaks prevent proper sensor readings.
- 3
Check Corroded or damaged connector — The sensor connector develops corrosion, loose pins, or water intrusion that breaks the electrical circuit. This prevents proper signal transmission.
- 4
Check Damaged wiring or faulty PCM — Wiring harness damage, breaks, or short circuits in the sensor circuit can cause signal loss. In rare cases, PCM programming errors or failure cause the code.
How to Fix It
- 1
Replace brake booster pressure sensor
Disconnect the sensor connector, unbolt the sensor from the brake booster, and install a new OEM or quality aftermarket sensor. Reconnect the electrical connector and test for code clearing.
- 2
Inspect and repair vacuum lines
Visually inspect all vacuum hoses connected to the brake booster for cracks, splits, or loose connections. Replace damaged hoses and secure loose connections with hose clamps.
- 3
Clean or replace sensor connector
Disconnect the sensor connector and inspect for corrosion or water damage. Clean contacts with electrical contact cleaner and dielectric grease, or replace the connector if severely damaged.
- 4
Check wiring and PCM
Use a multimeter to test continuity and voltage in the sensor wiring circuit. If wiring tests pass, scan for additional codes and consult technical service bulletins for potential PCM reprogramming or replacement.
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