C0547 code meaning
Vacuum Sensor Supply Voltage Circuit/Open
What C0547 means
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.
C0547 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C0547
- Brake system or ESC warning shown
- Stop-start inactive or electric vacuum pump running constantly
Common causes of C0547
- Most likelySupply wire or connector pin interrupted
- PossibleSupply line shorted to ground or another circuit
- Less likelyVacuum sensor shorting the supply internally
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Vacuum sensorSensor supply
What each part of C0547 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 47 | The exact fault in that area. |
What to do next
- Note C0547 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about C0547
What does C0547 mean?
C0547 means "Vacuum Sensor Supply Voltage Circuit/Open". Fault in the feed circuit powering the vacuum sensor on the brake booster, usually an open or a short on the regulated supply. It is a generic code, so it means the same on every make.
Is it safe to drive with C0547?
Drive gently and only to a workshop. With C0547 the car can go into limp mode (reduced power) to protect itself.
Will C0547 fail an emissions test?
C0547 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C0547 to fix?
Difficulty: medium. A typical repair takes 0.3 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will C0547 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.