P0559 — Brake Booster Pressure Sensor Circuit Intermittent

Does P0559 mean the brake booster itself has failed?

Not necessarily. P0559 specifically points to an intermittent brake booster pressure sensor circuit fault, so the wiring, connector, sensor, ground, and reference supply should be tested before replacing the booster.

Is it safe to drive with P0559 stored?

Driving may be possible if the brakes remain normal, but inconsistent assist or disabled convenience systems warrants prompt diagnosis. Stop driving if the pedal becomes hard or the brake booster does not hold pressure.

Why does P0559 sometimes stay in history?

The circuit may fail only during vibration, heat, or harness movement. Once the connection becomes stable again, the control module can retain P0559 as a history code even though the symptom is temporarily gone.

Will clearing P0559 with an ELM327 solve the problem?

No. An ELM327 or AIScanAuto scan tool can confirm and clear P0559, but clearing does not repair the sensor circuit. The code can return until the wiring, connector, or sensor is corrected.

When your engine control module detects a signal from the brake booster pressure sensor that keeps flickering in and out, it logs trouble code P0559. The official description for this OBD2 code reads "Brake Booster Pressure Sensor Circuit Intermittent." The module continuously watches this circuit while you drive. Whenever the sensor signal falls outside the acceptable window for a set number of consecutive drive cycles, P0559 gets stored and the check engine light illuminates.

The word "intermittent" tells you the problem isn't constant—the module receives correct readings some of the time, but something keeps causing the signal to drop out or spike unexpectedly. These ghost faults usually stem from physical problems in the wiring or connections. A pin that's slightly backed out, a wire broken beneath intact insulation, or a connector whose grip has weakened will all behave perfectly fine until vibration or temperature changes push them past their breaking point. When you pull the freeze frame data saved alongside P0559, you'll see exactly what the engine was doing—RPM, load, temperature, and vehicle speed—when the fault first appeared. That snapshot is your most useful clue for tracking down an intermittent problem.

Common Symptoms

• Check Engine Light stays illuminated or flickers on and off
• Noticeable drop in engine power; acceleration feels sluggish
• Vehicle may enter reduced-power limp-home mode
• Unusual whistling or hissing sounds from the engine bay
• Black smoke visible from the exhaust under hard acceleration
• Some drivers report increased oil consumption

Likely Causes

• Loose, corroded, or backed-out connector at the brake booster pressure sensor
• Wire broken underneath intact insulation—looks fine on the surface
• Connector pins making poor contact due to heat cycling
• Faulty or stuck boost control solenoid (if equipped)
• Cracked or disconnected vacuum lines feeding the brake booster circuit
• Worn or failing turbocharger components (on forced-induction engines)
• Clogged intake elements or exhaust restrictions (DPF/catalytic converter)

How to Diagnose

1. Hook up an OBD2 scanner and confirm P0559 is currently stored. Capture the freeze frame data—this shows the exact operating conditions when the module first detected the fault.
2. Check for any related trouble codes. Companion codes pointing to boost pressure, vacuum leaks, or sensor питание circuits often reveal the root cause faster than chasing P0559 alone.
3. Visually trace the wiring harness from the brake booster pressure sensor. Look for chafing, melted insulation, corrosion, or any signs the connector housing is cracked or contaminated.
4. Reproduce the fault mechanically. With the engine running and scanner monitoring live data, gently wiggle the harness and tap the sensor connector. Intermittent faults almost always surface under vibration stress.
5. Pressure-test the vacuum lines and boost plumbing if your vehicle uses forced induction. Leaks at the intercooler, couplings, or clamps are surprisingly common and can trigger P0559 indirectly.
6. Command the boost control solenoid (if applicable) with your scanner and verify that wastegate or bypass valve movement matches expectations.
7. Clear P0559, then drive through the conditions captured in your freeze frame data. If the code returns, you have confirmed the fault and narrowed your search area.

Repair Options and Costs

• Replace faulty brake booster pressure sensor: $80–$200
• Repair vacuum or boost leak (hoses, clamps, intercooler): $100–$400
• Replace boost control solenoid or actuator: $200–$600
• Turbocharger replacement (if confirmed failed): $1,200–$3,500

Total repair costs for P0559 typically fall between $100 and $600 when the issue is wiring or a vacuum leak. Turbo replacement—the most expensive scenario—rarely represents the first logical step. Proper diagnosis before purchasing parts almost always pays for itself.

Can You Drive with P0559?

Severity: CAUTION. The brake booster depends on consistent vacuum to assist your brakes. With P0559 active, your power brake assist may be reduced or unpredictable, especially under hard braking. Combine that with potential limp-home mode and reduced power, and you have a situation where safe operation cannot be guaranteed. Drive conservatively, avoid aggressive maneuvers, and schedule diagnosis promptly. Neglecting an intermittent boost or vacuum fault risks overheating the engine and causing far costlier damage down the line.

Related OBD2 codes

• P0500: Vehicle Speed Sensor "A" Malfunction
• P0501: Vehicle Speed Sensor "A" Range/Performance
• P0502: Vehicle Speed Sensor "A" Low Input
• P0503: Vehicle Speed Sensor "A" Intermittent/Erratic/High
• P0504: Brake Switch "A"/"B" Correlation
• P0505: Idle Control System Malfunction