C057EBrake Booster Temperature Sensor A/B Correlation
- Generic OBD-II code · Chassis
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- With two temperature sensors in the booster the module can cross-check them: after a long rest both should be close to ambient, and under load they should move in a consistent pattern. C057E is set when sensors A and B disagree beyond a plausible margin. GM fits two such channels in its booster (A: P25C6/P25C7, B: C0579/C057A), but its public tables do not list C057E, and no other maker documents it either. The idea is known from related systems: Safran compares redundant temperature sensors in electric brake actuators and discards inconsistent ones, and Hitachi Astemo's electric booster carries separate motor and drive circuit sensors. As the module cannot tell which reading is wrong, it usually protects the motor by reducing assist.
- What you may notice
- Brake system warning with service message
- Temperatures A and B clearly apart on the scan tool after a cold start
- Reduced brake assist
- Likely causes
- LikelyOne of the two thermistors drifted or lost thermal contact
- PossibleAdded resistance in one sensor circuit, e.g. corroded contact
- RareReal local overheating of motor or power stage, e.g. after jammed mechanics
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.