What does it mean?
P1576 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Brake Booster Vacuum Sensor Circuit High Input .
Symptoms
- Check engine light on with the fault stored
- Automatic stop-start function disabled and a message shown on the display
- The module may raise idle speed unnecessarily to generate vacuum, so the engine idles higher than normal
- Cruise control and some assistance functions may be unavailable
- Brake pedal feel is usually normal, since the fault is in the sensing circuit rather than the booster itself
- Slightly increased fuel consumption from the raised idle
Likely causes
- Signal wire shorted to the 5 V reference or to battery voltage inside a damaged connector
- Open sensor ground, which lets the signal float to the top of its range
- Internally failed vacuum sensor stuck at maximum output
- Water ingress and corrosion in the sensor connector, which sits in an exposed area on the booster
- Chafed harness where it runs across the bulkhead
- Sensor pushed out of its seal or fitted incorrectly after previous work
- Faulty sensor input circuit inside the control module
How to fix it
- With the ignition on and the engine off, compare the sensor reading in live data against atmospheric pressure
- Unplug the sensor and observe whether the value moves to its opposite extreme, which separates wiring from sensor faults
- Measure the 5 V reference and the sensor ground at the harness connector
- Test the signal wire for a short to reference or battery voltage with both ends disconnected
- Apply a known vacuum with a hand pump and watch the value track smoothly in live data
- Inspect the connector for water and corrosion, dry it out and repair the terminals
- Replace the sensor once the wiring proves good, then clear the code and confirm the reading matches actual vacuum