Brake Booster Pressure Sensor Circuit Intermittent
The P0559 code indicates an intermittent fault in the brake booster pressure sensor circuit. This sensor monitors vacuum or pressure in the brake booster to assist braking. An intermittent signal can cause unpredictable brake assist, potentially leading to hard brake pedal or increased stopping distance. The issue may stem from wiring, connector problems, or a failing sensor.
01. Most Common Causes
- Faulty brake booster pressure sensor
- Damaged or corroded wiring/connectors in the sensor circuit
- Intermittent short or open in the circuit
- Loose or poor electrical connection
02. Symptoms You Will Notice
- Intermittent hard brake pedal
- Brake warning light or check engine light on
- Reduced brake assist or longer stopping distance
- Erratic brake pedal feel
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data to capture conditions when fault occurred.
Step 2: Visually inspect the brake booster pressure sensor connector and wiring for damage, corrosion, or loose connections.
Step 3: Use a multimeter to test sensor signal voltage and compare to manufacturer specifications; check for intermittent opens or shorts by wiggling harness.
Step 4: If wiring is intact, replace the brake booster pressure sensor and clear codes; test drive to verify repair.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended because intermittent brake assist can lead to sudden hard pedal or reduced braking performance, increasing accident risk.
How much does it cost to fix?▼
Typically $50-$150 for a DIY sensor replacement; labor at a shop may add $50-$100, totaling $100-$250.