Chassis, generic

C057B Brake Booster Temperature Sensor B Circuit/Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C057B is defined for an interrupted circuit of booster temperature sensor B. No manufacturer publishes it; GM maps the faults of this channel to C0579 and C057A only. Temperature sensors of this kind are normally NTC thermistors placed near the motor or on the power stage and read through a voltage divider. If the thermistor or one of its wires opens, the divider node is pulled toward the excitation voltage, and a thermistor design guide advises placing diagnostic thresholds beyond the usable temperature range to catch that. Microchip points out that an NTC on a power module follows case and heatsink temperature rather than the chip junction. Because the sensor is usually inside the booster, an open circuit often means replacing the unit.

Likely causes

Open wire or loose pin between thermistor and booster electronics
Cracked thermistor body or broken lead after thermal or mechanical stress
Failed solder joint on the booster circuit board

Symptoms

  • Brake system warning and service message
  • Temperature B missing or at an extreme value on the scan tool
  • Assist possibly limited to protect the motor

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

C0579C057AC057CC057DP25C4

References: passive-components.eu, ww1.microchip.com, patents.google.com.