C0047: Brake Booster Pressure Sensor
What to do
The brakes work, but the pedal may become harder in some situations — repeated braking downhill, or just after the engine has stopped and restarted at a junction. Leave more room and be ready to press harder. Worth diagnosing soon.
What this code means
The brake booster pressure sensor circuit has a fault.
This sensor measures the vacuum, or the pressure, that the booster has available to assist with — not the pressure in the brake lines.
Knowing the reserve is what lets the car act before the driver notices. A vacuum booster stores enough for a few applications with the engine off; when the reading falls the car can run the vacuum pump, or on a hybrid restart the engine, specifically to keep the pedal light. Losing the reading means those responses stop happening.
So the first thing a driver may notice is a harder pedal in exactly the situations the car used to manage — repeated braking down a long hill, or moving off after a stop-start engine shutdown.
Distinguish it from the brake pressure sensors at C0044. Those read hydraulic pressure the driver has created. This one reads the assistance available to create it.
Likely causes
Start here
- Faulty brake booster pressure sensor · specialist
- Corroded or loose connector · specialist
- Leaking brake servo or servo hose · specialist
- Damaged wiring harness · specialist
Less common
- Faulty stability control module · specialist
Symptoms
Components involved
Information, not instruction
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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
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