C057A code meaning
Brake Booster Temperature Sensor B Circuit High
Chassis system Generic code C05xx codes Check engine light
What C057A means
C057A is the high counterpart: temperature channel B of the booster reads at its upper end, which GM interprets as the signal shorted to supply. GM's 2023 and 2025 EBCM tables set it above 3.14 V when five checks in a row fail within 0.6 s and rate it Type B, with MIL after two trips; the 2019 Cadillac XT4 version uses 3.34 V and is Type C without MIL. Channel A trips at 3.27 V under P25C7, so the two channels have slightly different limits. Whether a high voltage means hot or cold depends on where the thermistor sits in its divider, which is why the module treats a value at the rail as a wiring fault rather than a temperature. Without a usable reading the booster cannot protect its motor and may reduce assist.
C057A at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C057A
- Check engine light after two trips (GM 2023/2025) and brake warning
- Temperature B reading stuck at a limit
- Reduced brake assist during long downhill braking
Common causes of C057A
- Most likelyTemperature signal B shorted to the sensor supply or another voltage
- PossibleThermistor or its return line open, pulling the input to the rail
- Less likelyMoisture or corrosion inside the booster electronics
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 C057A means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 7A | The exact fault in that area. |
What to do next
- Note C057A 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 C057A
What does C057A mean?
C057A means "Brake Booster Temperature Sensor B Circuit High". C057A is the high counterpart: temperature channel B of the booster reads at its upper end, which GM interprets as the signal shorted to supply. It is a generic code, so it means the same on every make.
Is it safe to drive with C057A?
Drive gently and only to a workshop. With C057A the car can go into limp mode (reduced power) to protect itself.
Will C057A fail an emissions test?
C057A 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 C057A to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will C057A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.