P0559: Brake Booster Pressure Sensor Circuit Intermittent
What to do
Driveable, but note whether the brake pedal ever feels harder than usual, and when. A pedal that changes feel is a vacuum problem rather than a wiring one, and matters more.
What this code means
The brake booster pressure signal drops out intermittently. Worth distinguishing from a genuinely intermittent vacuum supply, which a failing vacuum pump produces — a pump that works when cold and struggles when hot gives a fault that appears after twenty minutes of driving and clears overnight.
If pedal effort varies noticeably along with the code, the vacuum is the problem rather than the signal.
Likely causes
Start here
- Corroded or loose connector · easy
- Intermittent open in sensor wiring · moderate
- Faulty brake booster pressure sensor · moderate
Less common
- Faulty vacuum pump · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P0559.