C0279 code meaning
Brake Booster Boost Sensor Circuit Malfunction
What C0279 means
C0279 is absent from every publicly available J2012 list, and no maker describes it as a booster sensor code. GM does use the number: its bulletin PIP5094 names it among the chassis keywords for 2014 and older cars and light trucks, and the GM brake code chart published by AA1Car renders it as Powertrain Configuration Not Valid, meaning the brake module received engine or driveline data it was not set up for. The part in the title reports how much vacuum or boost pressure the brake booster holds. On the 2011 Saab 9-4X the brake module feeds such a sensor with 5 V and switches an electric vacuum pump on when the reading drops; Bosch uses the same signal for start/stop and brake assist. With the circuit faulty, the module loses that reading.
C0279 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C0279
- Brake or ABS warning lamp on
- Electric vacuum pump runs constantly or not at all
- Start/stop or brake assist unavailable
Common causes of C0279
- PossibleOpen or shorted 5 V supply, signal or ground wire of the booster sensor
- PossibleBooster pressure sensor failed or its grommet leaking
- Less likelyBrake module not configured for the fitted engine or driveline (GM meaning of the number)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Brake boosterBooster pressure sensorBrake control module
What each part of C0279 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 79 | The exact fault in that area. |
What to do next
- Note C0279 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 C0279
What does C0279 mean?
C0279 means "Brake Booster Boost Sensor Circuit Malfunction". C0279 is absent from every publicly available J2012 list, and no maker describes it as a booster sensor code. It is a generic code, so it means the same on every make.
Is it safe to drive with C0279?
C0279 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will C0279 fail an emissions test?
C0279 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 C0279 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will C0279 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.