C0547Vacuum Sensor Supply Voltage Circuit/Open
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- Fault in the feed circuit powering the vacuum sensor on the brake booster, usually an open or a short on the regulated supply. Such sensors need a stable 5 V: HELLA specifies 4.5 to 5.5 V for its three-pin vacuum sensor (output, ground, supply), whose analogue signal tells the brake control unit when to run the electric vacuum pump. Bosch describes the same sensor as the basis for pump control, stop-start and ESP assistance. A Saab 9-5 brake module shows how a supply is policed on a brake sensor: outside 4.4 to 5.6 V lasting 0.06 s is a fault. No maker documents C0547 publicly. Without valid supply the vacuum value is lost, so assist functions and an electric pump may run on fallback. C0548 is the narrower case of a supply that is merely too low.
- What you may notice
- Brake system or ESC warning shown
- Stop-start inactive or electric vacuum pump running constantly
- Likely causes
- LikelySupply wire or connector pin interrupted
- PossibleSupply line shorted to ground or another circuit
- RareVacuum sensor shorting the supply internally
- Repair
- Medium · Often possible to do yourself.Typical cost: €30 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.