P2526: Vacuum Reservoir Pressure Sensor Circuit Range/Performance
What to do
Take the brake pedal seriously with this one — this code often means the stored vacuum genuinely is low rather than that the sensor is wrong, and stored vacuum is what makes the brake servo work. If the pedal is harder than usual, have the car recovered rather than driven. Ask for the vacuum to be measured with a gauge and for it to be watched after switch-off: a store that drains away has a leaking check valve or hose, which is cheap to fix.
What this code means
The stored vacuum reading is electrically valid but does not match what the module expects.
This is the variant most likely to be reporting a genuine loss of vacuum rather than a sensor fault, because the quantity being measured is physical and easily verified. A reservoir that will not hold vacuum, or a pump that cannot replenish it fast enough, produces exactly this while every wire is intact.
The distinguishing test costs almost nothing: measure the vacuum at the reservoir with a gauge, and see whether it holds after the engine is switched off. A store that decays quickly has a leak, and the check valve is the first place to look. A store that never reaches its figure points at the pump.
The brake consequence at P2525 applies with more force here, since this code describes a store that is actually inadequate rather than a circuit the module cannot read.
Likely causes
Start here
- Failed vacuum check valve · easy
- Disconnected or leaking vacuum hose · easy
- Faulty vacuum pump · moderate
Less common
- Leaking vacuum reservoir · moderate
- Leaking brake servo or servo hose · moderate
- Faulty vacuum reservoir pressure sensor · easy
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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