What it means
The brake booster temperature sensor A and B readings do not agree as expected. The code alone does not identify which sensor or circuit is at fault.
At a glance
- Usually lights the ABS or stability-control warning light
How it works
The brake control module compares temperature readings from brake booster sensors A and B. C057E sets when those two readings do not agree as expected; either sensor, its circuit, or the module may be responsible, so the comparison alone does not identify the faulty side.
Common causes
Most likely first.
- One temperature sensor reading has drifted
- Faulty temperature sensor
- Wiring or connector fault
- Control module fault
Symptoms
- Brake or ABS warning light
- Brake booster functions may be limited
How to diagnose it
- Read freeze-frame data and compare live readings from sensors A and B under the same conditions to see which reading differs or changes implausibly.
- Inspect both sensors' connectors and wiring for corrosion, loose terminals, chafing, or damage that could affect the comparison.
- Check the mounting and connections of both sensors, since a loose sensor can respond differently from the other.
- Test the A and B sensor circuits and compare each sensor's output with the manufacturer's specification.
- If both sensor signals and circuits pass, follow the manufacturer's procedure to check the control module's comparison logic.
Common fixes
- Secure a loose sensor A or B connector or mounting.
- Clean or repair corroded terminals and damaged wiring on the affected sensor circuit.
- Replace the sensor whose output fails the manufacturer's specification.
- Correct sensor mounting if it causes the A/B readings to diverge.
- Repair or replace the control module only if both sensor circuits test correctly and the manufacturer's procedure identifies a module fault.
Can I keep driving?
If braking feels normal, drive cautiously and have the brake booster system checked because its functions may be limited. Stop safely if brake assist changes, the pedal becomes unusually hard, or another brake warning appears.
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.