P2528: Vacuum Reservoir Pressure Sensor Circuit High
What to do
This is the reading an empty vacuum reservoir produces, so treat a hard brake pedal as the real thing until proven otherwise — have the car recovered rather than driven. A split hose, a failed check valve or a stopped vacuum pump all produce this genuinely. Ask for the vacuum to be measured at the reservoir before the sensor is replaced.
What this code means
The vacuum reservoir sensor circuit reads above its valid range — an open circuit, a disconnected sensor, or a reported pressure at or above atmospheric.
By the convention set out at P2527, a high reading means no vacuum at all. That is entirely possible as a real condition rather than a circuit fault: a reservoir open to atmosphere through a split hose or a failed check valve reads exactly this, and so does a vacuum pump that has stopped working.
So this variant should not be assumed to be wiring. It is the reading a genuinely empty reservoir produces, and an empty reservoir means no brake assistance beyond what the servo itself holds.
Likely causes
Start here
- Disconnected or leaking vacuum hose · easy
- Failed vacuum check valve · easy
- Faulty vacuum pump · moderate
- Open circuit in sensor wiring · moderate
Less common
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
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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