P2527: Vacuum Reservoir Pressure Sensor Circuit Low
What to do
Check how the brake pedal feels; if it is harder than usual, have the car recovered. You may also hear the vacuum pump running more than usual, which is the module not being able to tell whether it has enough. Ask for the connector to be inspected before the sensor is replaced.
What this code means
The vacuum reservoir sensor circuit reads below its valid range, normally a short to ground.
Worth being clear about which direction means what, because vacuum sensors invite confusion: these report absolute pressure, so a low pressure reading corresponds to a high vacuum. A circuit reading below its valid range is therefore claiming a vacuum stronger than the pump could produce, which is why the module treats it as a circuit fault rather than a good result.
The practical consequence is that the module cannot tell whether it has vacuum, so it will generally run the pump more than necessary — audible on some vehicles as a pump that runs continuously.
Likely causes
Start here
- Wiring shorted to ground · moderate
- Faulty vacuum reservoir pressure sensor · easy
- Corroded or loose connector · easy
Less common
- Damaged wiring harness · moderate
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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