C057CBrake Booster Temperature Sensor B Circuit Range/Performance
- Generic OBD-II code · Chassis
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- C057C covers a temperature B value that is electrically valid but behaves implausibly – it stays frozen, climbs too slowly after hard use, or departs from what the module's thermal estimate predicts. No manufacturer documents this code publicly. In Hitachi Astemo's electric booster patent the measured motor and drive circuit temperatures decide when current and thus assist are limited and when they are restored, with an intermediate step if the pedal is still pressed; a wrong but believable value would therefore throttle assist too early or let the motor run too hot. Thermistor makers name moisture, cracking, solder stress and resistance drift as typical long-term failures. The module may restrict assist as a precaution.
- What you may notice
- Brake warning, often after long or repeated braking
- Temperature B frozen or lagging behind temperature A
- Assist reduced earlier than usual
- Likely causes
- LikelyThermistor resistance drifted through age, moisture or heat cycling
- PossibleSensor lost thermal contact with motor or power stage
- RarePlausibility model in the booster software too strict
- 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.