P258B: Vacuum Pump Control Circuit A Range/Performance
What to do
Take this one seriously and get it looked at promptly. The brakes still work, but the servo that multiplies your pedal effort may not — so the pedal can feel very hard and the car needs considerably more distance to stop.
Leave more room than usual and brake earlier until it is repaired. If the pedal is already hard, press it much more firmly than feels normal — the brakes will still stop the car, they simply need the effort the servo was providing.
Ask for the vacuum hoses and the check valve to be checked before the pump is replaced. A perished hose or a leaking valve is far commoner and much cheaper.
Mention whether the pedal is hard from the first press of the day, or only sometimes. That distinction genuinely narrows the diagnosis.
What this code means
The vacuum pump is being commanded but not producing the vacuum expected of it.
Why a car needs a vacuum pump at all is the thing to understand here, and it explains why this code is safety-relevant. A brake servo multiplies pedal effort using vacuum. A traditional petrol engine makes plenty in its intake manifold — but a diesel has no throttle plate to create it, a turbocharged petrol makes little at part throttle, a stop-start car has the engine off at junctions, and an electric vehicle has no engine at all. All of them use an electric vacuum pump instead.
So this code concerns the brakes. Losing vacuum does not make the brakes fail — the hydraulics still work — but the servo stops assisting, so the pedal goes hard and stopping the car takes far more effort than the driver is used to. The distance needed rises sharply, which is the part that matters.
Range/performance means the pump runs and the vacuum does not appear, which points at three things:
- A leak in the vacuum circuit — a perished hose, a failed servo diaphragm, or a check valve not sealing. Check these before the pump; they are far commoner and much cheaper.
- A worn pump, whose vanes or diaphragm no longer seal.
- A vacuum sensor misreporting, in which case the vacuum is fine.
A hard pedal that improves after the engine has been running is the classic report, and it is worth acting on immediately.
Likely causes
Start here
- Faulty vacuum pump · moderate
- Failed vacuum check valve · easy
- Leaking brake servo or servo hose · moderate
Less common
- Leaking brake booster diaphragm · specialist
- Faulty brake booster pressure sensor · moderate
Symptoms
Components involved
Information, not instruction
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