P0559 low

Brake Booster Pressure Sensor Circuit Intermittent

The P0559 code means the vehicle's onboard diagnostic system has detected: Brake Booster Pressure Sensor Circuit Intermittent. This is a low severity code.

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Keep driving?: Yes, but fix soon
DIY difficulty: moderate
Estimated cost: $50 - $300 (parts and labor)

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Common Symptoms

Check Engine Light on
Start/stop system intermittently disabled
Occasional idle speed variation
Intermittent brake booster warning

Probable Causes (Ranked by Likelihood)

Loose brake booster pressure sensor connector Very High
Intermittent wiring break in sensor circuit High
Sensor with marginal internal connection Moderate
Vibration-induced signal dropout Moderate

Step-by-Step Diagnostic Procedure

Wiggle the sensor connector while monitoring live data for signal dropouts
Inspect wiring for damage at flex points and connectors
Monitor sensor signal with a data logger over extended driving to capture intermittent events
Check connector pin tension and clean with electrical contact cleaner

Frequently Asked Questions

What causes an intermittent brake booster sensor signal?

The most common cause is a loose connector that momentarily loses contact due to engine vibration. Corrosion on connector pins can also cause intermittent signal loss. The sensor location on the brake booster is subject to significant vibration.

Is P0559 urgent to repair?

P0559 is not urgent as the brake system continues to function normally. However, it may intermittently disable the start/stop system and the ECM cannot reliably monitor brake booster vacuum during intermittent events.

Can I fix an intermittent connection myself?

Often yes. Start by disconnecting and reconnecting the sensor connector to re-seat the pins. Clean the pins with electrical contact cleaner. If the connector is damaged, repair or replace the connector pigtail.