P2525

Vacuum Reservoir Pressure Sensor Circuit

Severity: High
Driving: Drive only to a garage

A fault in the vacuum reservoir pressure sensor circuit. A vacuum reservoir stores vacuum so it is available when the engine is not making much - at full throttle, or on a diesel, which produces very little. On many vehicles that store feeds the brake servo.

Possible causes

CommonSplit, perished or disconnected vacuum hose
CommonFailed non-return valve on the reservoir
CommonFailed vacuum pump, on engines that use one
CommonFailed pressure sensor
PossibleCorroded connector or damaged wiring
PossibleCracked or corroded reservoir

What you might notice

Brake pedal harder than usual
More pedal effort needed to stop
Hissing from the pedal area
Vacuum-operated actuators not working
Check engine light on

What to check, in order

Test the brake pedal before driving. With the engine off, press it several times to use up the stored vacuum, then start the engine with your foot on the pedal - it should sink slightly as assistance arrives. If it does not, assistance is genuinely missing.
Check the vacuum hoses and the non-return valve for splits, looseness and perishing.
On a diesel or a direct-injection petrol engine, check the vacuum pump - these engines make little vacuum of their own and depend on it.
Inspect the sensor connector for corrosion.
Check the reference voltage and earth at the sensor.

Read this code from your own car

Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.

Get Pin16 on Google Play

Where this code sits

B · Body C · Chassis P · Powertrain U · Network and communication

Vehicle speed control, idle control and auxiliary inputs