What it means
The vacuum pump control circuit is electrically intact, but the pump response does not match the model — pump runs longer than expected to reach setpoint, current draw rises (mechanically tight) or vacuum does not build at all. Aged motor brushes, dry vanes or a leaking line are typical causes.
At a glance
- Usually lights the check-engine light
How it works
An electric vacuum pump supplies brake-booster vacuum when engine vacuum is insufficient or unavailable. The control circuit is responding electrically, but the module detects that pump performance does not match what it expects, such as slow vacuum buildup or poor pump response. Reduced vacuum can make the brake pedal harder and lower brake assist, especially after repeated stops.
Common causes
Most likely first.
- Aged motor brushes or dry vanes
- Leaking vacuum line
- Sensor element aged beyond calibration window
Symptoms
- Brake warning light may come on
- Brake pedal may feel harder than usual
- Brake assist may be reduced, especially after repeated braking
How to diagnose it
- Check for a hard pedal or brake warning first, and avoid driving if braking effort is clearly increased.
- Read freeze-frame and live pump command, run-time, and vacuum data to see whether the pump runs too long or fails to reach its expected vacuum.
- Inspect the vacuum hoses and connections for cracks, disconnections, or leaks that could prevent vacuum from building.
- Inspect the pump connector and wiring for damage, then check pump current and vacuum response using the manufacturer's procedure.
- If the hoses and electrical supply are sound, test the pump and vacuum sensing system to identify a weak pump or inaccurate feedback.
Common fixes
- Reconnect a loose vacuum hose or repair a leaking line.
- Repair a damaged pump connector or wiring connection.
- Replace a worn electric vacuum pump if it cannot produce adequate vacuum.
- Replace a confirmed faulty vacuum sensor or feedback component.
Can I keep driving?
Avoid repeated hard braking and do not drive if the pedal is hard or brake assist is reduced; arrange prompt repair or safe recovery. A weak pump or vacuum leak can leave less assist during successive stops.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.