P0559: Brake Booster Pressure Sensor Circuit Intermittent

The brake booster pressure sensor (5 V reference, signal, ground) measures the vacuum in the brake booster. On direct-injection, turbo, stop-start and hybrid engines intake vacuum is scarce, so the engine module watches it and creates vacuum when needed – closing the throttle, suppressing engine stop or running an electric vacuum pump. That makes it an input to idle and throttle control. P0559 means the signal jumps briefly – a loose contact or broken wire under movement – without staying out of range long enough for P0557 or P0558. No manufacturer document available to us uses it; GM catches dropouts through the sample counters of P0557/P0558. CARB requires input components to be checked for circuit faults.

Symptoms

• Warning comes and goes
• Stop-start inactive at times
• Check engine light (depending on the maker)

Most likely causes

• Loose contact at the sensor connector (pin tension, corrosion)
• Broken or chafed wire moving with the engine
• Sensor with internal dropouts

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the hoses, clamps, and intercooler
2. Gently move the wiring with the engine running and watch whether the reading changes.
3. Compare commanded and actual pressure in live data
4. Check the actuator's movement
5. Check the vacuum hoses and the solenoid valve
6. Check the oil and the turbo shaft play before replacing it

Good to know

• Repair difficulty: medium

What each character of P0559 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 5: Speed and idle
• 59: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0559?

Drive without demanding power and go to a repair shop soon. If you see a lot of blue smoke or hear a metallic noise, shut off the engine.

What causes code P0559?

The most common causes are: loose contact at the sensor connector (pin tension, corrosion); broken or chafed wire moving with the engine; sensor with internal dropouts.

Related codes

• P0555Brake Booster Pressure Sensor Circuit
• P0556Brake Booster Pressure Sensor Circuit Range/Performance
• P0557Brake Booster Pressure Sensor Circuit Low
• P0558Brake Booster Pressure Sensor Circuit High

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 18OBDG03A Engine Diagnostics

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.