P0555 — Brake Booster Pressure Sensor Circuit #

Note: The wording for this code may vary depending on the vehicle manufacturer (OEM). Always refer to your OEM documentation for specific descriptions.

• Brake Booster Pressure Sensor Circuit Malfunction (General/SAE)
• Brake Booster Pressure Sensor “A” Circuit (Ford, GM)
• Brake Booster Sensor Circuit Range/Performance (Volkswagen/Audi)
• Brake Vacuum Pressure Sensor Circuit Fault (Hyundai/Kia)

Summary of DTC P0555 #

DTC P0555 signals an anomaly detected by the vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) in the brake booster pressure sensor circuit. The brake booster, sometimes called a vacuum servo, multiplies the force from your foot to the brakes, making stopping easier and safer. The pressure sensor monitors the vacuum or pressure inside the booster and relays this data to the ECM/PCM, which uses it for safety and emissions functions. If the sensor’s output is outside of the expected range, or if the circuit shows voltage that’s too high, too low, or erratic, code P0555 will be stored. This fault can lead to changes in brake feel, reduced braking assistance, or even trigger warning lights related to braking or stability systems.

Common symptoms for DTC P0555 #

When code P0555 appears, you’ll likely notice changes in how your brakes feel and in dashboard alerts. Depending on the vehicle and the severity of the issue, symptoms may be subtle or quite pronounced. It’s important not to ignore these signs, as the brake booster is a critical safety component.

• Brake warning light or Check Engine Light (CEL) illuminated
• Increased brake pedal effort (hard pedal)
• Hissing noise from the brake booster area
• Reduced braking assistance, especially at low speeds
• Occasional ABS or stability control warnings
• Rough engine idle (in severe vacuum leak cases)

Most Likely Causes for DTC P0555 #

P0555 can result from various issues in the brake booster pressure sensor circuit. Some causes are more common than others. Identifying the root cause quickly will save time and prevent unnecessary repairs.

1. Faulty brake booster pressure sensor: Sensor itself is defective.
2. Damaged, corroded, or loose sensor wiring/connectors: Electrical issues are frequent culprits.
3. Vacuum leak in the brake booster or related hoses: Loss of vacuum affects sensor readings.
4. Failed or leaking brake booster: Internal failure impacts pressure/vacuum signal.
5. Faulty ECM/PCM (rare): Module misinterprets or fails to process sensor input.

Step-by-step diagnostic guide for DTC P0555 #

Tackling P0555 requires a systematic approach. A proper diagnostic procedure helps avoid replacing good parts and ensures safe brake operation. Here’s a recommended step-by-step process:

• 1. Scan for codes and freeze frame data. Document all related codes and operating conditions when P0555 was set.
• 2. Check for Technical Service Bulletins (TSBs). Sometimes, OEMs release updates for known sensor or wiring faults.
• 3. Visually inspect the brake booster, vacuum lines, and sensor wiring. Look for loose, corroded, or damaged connectors, as well as cracked hoses.
• 4. Test brake booster pressure sensor output. Using a multimeter or scan tool, check for expected voltage or data readings as specified by your OEM.
• 5. Check for vacuum at the booster. With the engine running, verify that sufficient vacuum is present at the booster inlet.
• 6. Wiggle test the wiring harness. Move the wires gently while monitoring live data for intermittent faults.
• 7. Replace or repair components as needed based on findings. Re-test the system after each step to confirm resolution.

Possible repairs for DTC P0555 #

Once the root cause is pinpointed, you can address P0555 with targeted repairs. Always use quality parts and follow OEM procedures to ensure reliability and safety.

• Replace the brake booster pressure sensor if found faulty.
• Repair or replace damaged wiring/connectors in the sensor circuit.
• Fix any vacuum leaks in hoses or fittings leading to the brake booster.
• Replace the brake booster assembly if it is leaking or internally failed.
• In rare cases, reprogram or replace the ECM/PCM per OEM guidance.

Is it safe to drive with DTC P0555? #

Limited: Caution is advised. While your brakes may still operate, a malfunction in the brake booster pressure sensor or its circuit can lead to increased pedal effort and reduced braking assistance. This can make it harder to stop quickly, especially in emergencies. If you experience a hard pedal, hissing noises, or reduced braking power, it is safest to have the vehicle inspected and repaired as soon as possible. Avoid highway speeds and heavy traffic until the issue is resolved.

Vehicles most commonly affected by DTC P0555 #

While P0555 is a generic OBD-II code, some makes and models are more prone to this fault due to sensor placement, wiring design, or brake booster construction. The following vehicles are frequently reported with this code:

• Ford F-150, Escape, Fusion (2010s)
• Chevrolet Silverado, Malibu (2010s)
• Hyundai Sonata, Santa Fe (2011–2018)
• Kia Optima, Sorento (2011–2018)
• Volkswagen Jetta, Passat (2012–2017)

Common mistakes & best practices for DTC P0555 #

Misdiagnosing P0555 can lead to wasted time and unnecessary expense. Here’s what to avoid—and some tips for success.

• Replacing the sensor without checking wiring or vacuum supply. Always verify circuit integrity and booster operation first.
• Ignoring related codes. Sometimes, other codes (vacuum, ABS, or stability) provide critical clues.
• Overlooking simple vacuum leaks. A cracked hose can mimic a sensor fault.
• Not clearing codes after repairs. Always clear codes and verify the fix with a road test and scan tool.
• Using non-OEM sensors. Some aftermarket parts may not meet OEM specs, leading to repeat issues.

Quick FAQ for P0555 #

Still have questions? Here are fast answers to what drivers and techs most often ask:

• Q: Can a faulty brake booster pressure sensor cause my brakes to fail completely?
  A: Not typically. You may lose power assist, making the pedal harder to press, but the brakes should still function mechanically.
• Q: Will clearing the code with a scan tool fix the problem?
  A: No. The underlying issue must be diagnosed and repaired. The code will return if the fault remains.