C054F code meaning
Vacuum Sensor B Circuit Low
What C054F means
The voltage from vacuum sensor B is lower than any value its characteristic allows. Taking HELLA's booster sensor as the reference, the output should never drop below 0.4 V, while 0.5 V corresponds to no vacuum at all; a reading underneath that is electrical rather than physical. A signal line grounded through chafing, a lost 5-V supply or a sensor with a dead output stage are the usual sources, and a low supply (C0548) can contribute. Mitsubishi's brake unit shows that short circuits on the brake vacuum sensor are caught within one second. Bosch lists pump control and stop-start among the functions fed by this measurement, so they fall back when it is lost. No maker documents C054F publicly. C0550 is the high fault, C054B the low fault of sensor A.
C054F at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyEasy, DIY possible
- Typical labor0.2 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C054F
- Brake assist warning shown
- Stop-start unavailable
Common causes of C054F
- Most likelySignal wire of sensor B grounded
- PossibleNo 5-V feed at sensor B
- Less likelyOutput stage of sensor B failed
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Vacuum sensor bSensor wiring
What each part of C054F means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4F | The exact fault in that area. |
What to do next
- Note C054F 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 C054F
What does C054F mean?
C054F means "Vacuum Sensor B Circuit Low". The voltage from vacuum sensor B is lower than any value its characteristic allows. It is a generic code, so it means the same on every make.
Is it safe to drive with C054F?
Drive gently and only to a workshop. With C054F the car can go into limp mode (reduced power) to protect itself.
Will C054F fail an emissions test?
C054F 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 C054F to fix?
Difficulty: easy. A typical repair takes 0.2 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will C054F clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.