C057B code meaning
Brake Booster Temperature Sensor B Circuit/Open
What C057B means
C057B is defined for an interrupted circuit of booster temperature sensor B. No manufacturer publishes it; GM maps the faults of this channel to C0579 and C057A only. Temperature sensors of this kind are normally NTC thermistors placed near the motor or on the power stage and read through a voltage divider. If the thermistor or one of its wires opens, the divider node is pulled toward the excitation voltage, and a thermistor design guide advises placing diagnostic thresholds beyond the usable temperature range to catch that. Microchip points out that an NTC on a power module follows case and heatsink temperature rather than the chip junction. Because the sensor is usually inside the booster, an open circuit often means replacing the unit.
C057B at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C057B
- Brake system warning and service message
- Temperature B missing or at an extreme value on the scan tool
- Assist possibly limited to protect the motor
Common causes of C057B
- Most likelyOpen wire or loose pin between thermistor and booster electronics
- PossibleCracked thermistor body or broken lead after thermal or mechanical stress
- Less likelyFailed solder joint on the booster circuit board
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Brake booster temp sensor bElectric brake booster
What each part of C057B means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 7B | The exact fault in that area. |
What to do next
- Note C057B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about C057B
What does C057B mean?
C057B means "Brake Booster Temperature Sensor B Circuit/Open". C057B is defined for an interrupted circuit of booster temperature sensor B. It is a generic code, so it means the same on every make.
Is it safe to drive with C057B?
Drive gently and only to a workshop. With C057B the car can go into limp mode (reduced power) to protect itself.
Will C057B fail an emissions test?
C057B is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C057B to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will C057B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.