Chassis, generic

C0579 Brake Booster Temperature Sensor B Circuit Low

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Electromechanical brake boosters watch the heat in their motor and power electronics so they can scale back assist before damage; a Hitachi Astemo patent, for example, describes one sensor on the motor and one in the drive circuit, with assist limited above set temperatures. GM reads two temperature channels from its booster: A under P25C6/P25C7, B under C0579/C057A. C0579 means channel B reads too low, which GM treats as a short to ground: under 0.03 V on five consecutive checks within 0.6 s in the 2023 and 2025 tables, Type B with MIL after two trips. GM's 2019 Cadillac XT4 tables use the same voltage with two detections between about 7 and 124 mph, but as Type C without MIL. The booster then runs a protective strategy.

Likely causes

Temperature signal B shorted to ground inside the booster or its harness
Thermistor shorted, e.g. after overheating
Fault in the booster control electronics reading the channel

Symptoms

  • Check engine light after two trips (GM 2023/2025), brake warning
  • Brake assist may be reduced as a precaution
  • Booster temperature B shows an implausible value on the scan tool

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–2,500
Time0.5–4 h

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

Parts involved

brake booster temp sensor belectric brake booster

Related codes

C057AC057BC057CC057DP25C6

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, patents.google.com.