Chassis, generic

C0279 Brake Booster Boost Sensor Circuit Malfunction

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Open or shorted 5 V supply, signal or ground wire of the booster sensor
Booster pressure sensor failed or its grommet leaking
Brake module not configured for the fitted engine or driveline (GM meaning of the number)

Symptoms

  • Brake or ABS warning lamp on
  • Electric vacuum pump runs constantly or not at all
  • Start/stop or brake assist unavailable

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€30–350
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

brake boosterbooster pressure sensorbrake control module

Related codes

C0273C0277C0267

References: static.nhtsa.gov, aa1car.com, saabwisonline.com, bosch-mobility.com.