Chassis, generic

C057D Brake Booster Temperature Sensor Circuit B Intermittent/Erratic

Check engine lightUsually off
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

C057D is meant for a temperature B signal that drops out or jumps for brief moments instead of failing for good – a loose connector pin, a cracked solder joint or a wire breaking under vibration are the classic reasons. No manufacturer publishes a threshold for it. GM's monitors for this channel require several consecutive out-of-range samples (two or five) before storing C0579 or C057A, which filters single spikes; a separate code for unsteady behaviour is not listed in GM's public tables. Thermistor suppliers name mechanical stress, moisture and solder damage as frequent sources of unstable readings. The fault tends to come and go with temperature or road shocks and may return after clearing; while the signal is unreliable the booster can limit assist.

Likely causes

Loose or fretting pin in the booster connector
Cracked solder joint of the thermistor on the circuit board
Moisture ingress causing leakage currents at the sensor

Symptoms

  • Brake warning that appears and disappears
  • Temperature B jumping on the scan tool
  • Code returns some time after clearing

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–2,500
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

C0579C057AC057BC057CP25C8

References: analogtechnologies.com, gsi.ext.gm.com, passive-components.eu.