What it means
The brake booster temperature sensor B signal is above the expected range. 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 supplies a signal used by the brake control system to monitor booster temperature. C057A sets when the signal is above its expected electrical range, which can be caused by a circuit fault or the sensor; the code alone does not identify which.
Common causes
Most likely first.
- Signal wire shorted to battery
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Brake or ABS warning light
- Brake booster functions may be limited
How to diagnose it
- Read the brake system's freeze-frame data and compare the live sensor B temperature reading with sensor A or other available temperature data to see whether B is consistently high.
- Inspect sensor B's connector and harness for a signal wire touching a battery-positive source, pinching, or heat damage.
- Check the connector pins for corrosion and poor contact, which can distort the signal.
- Using the wiring diagram and manufacturer's specification, test the signal circuit for a short to battery voltage and verify the supply and ground.
- If the wiring checks pass, test sensor B against the manufacturer's specification and evaluate the control module only after the sensor is ruled out.
Common fixes
- Clean and secure corroded or loose sensor B connector contacts.
- Repair a signal wire shorted to battery voltage.
- Repair pinched or heat-damaged wiring.
- Replace sensor B if its output fails the manufacturer's specification.
- Repair or replace the control module only if sensor and circuit checks pass.
Can I keep driving?
Drive cautiously only if braking and assist feel normal, and avoid demanding driving until the brake system is checked. If braking changes or the warning indicates reduced booster function, stop safely and arrange inspection.
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.