What it means
The brake booster temperature sensor B reading is outside the expected range or is implausible. The code alone does not identify whether the cause is the sensor or its circuit.
At a glance
- Usually lights the ABS or stability-control warning light
How it works
Brake booster temperature sensor B reports a temperature-related signal to the brake control system. C057C sets when the reading is outside the expected range or behaves implausibly, even if the circuit is not simply open or electrically high or low.
Common causes
Most likely first.
- Sensor reading drifted
- Sensor element aged beyond calibration window
- Sensor mounting loose - signal damping
Symptoms
- Brake or ABS warning light
- Brake booster functions may be limited
How to diagnose it
- Check freeze-frame data and compare sensor B's live reading with sensor A and the vehicle's operating conditions to determine whether B is implausible or changes too little.
- Inspect sensor B's mounting and connector for looseness, contamination, corrosion, or damage that could affect its reading.
- Check the harness for chafing or poor pin contact, then gently move the wiring while watching sensor B's live data for a signal change.
- Test sensor B's signal and circuit using the manufacturer's procedure and compare results with the manufacturer's specification.
- If the sensor and wiring pass, check whether the module or sensor mounting is causing the implausible reading before replacing parts.
Common fixes
- Secure a loose sensor B mounting or connector.
- Clean and repair poor electrical contacts or damaged wiring.
- Replace sensor B if its reading drifts outside the manufacturer's specification.
- Correct sensor mounting if it prevents the intended temperature response.
- Repair or replace the control module only if vehicle-specific tests confirm a module fault.
Can I keep driving?
If braking and booster assist feel normal, drive cautiously and have the fault checked soon; the warning may indicate that the system is limiting booster functions. Stop safely if assist changes or the brake pedal becomes unusually hard.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.