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DTC codes / C05xx · Brakes, steering and suspension / C057A

C057ABrake Booster Temperature Sensor B Circuit High

C057A means the antilock braking system (ABS) module has detected an abnormally high voltage on the signal circuit for the brake booster temperature sensor, identified as sensor B. The computer expects a voltage within a calibrated range that corresponds to a safe booster temperature, and a reading above that range sets this code.

SystemChassis
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaBrakes, steering and suspension

Symptoms you may notice

  • Illumination of the ABS warning light, often accompanied by the traction control and stability control lights
  • A brake warning light on the dashboard, depending on how the manufacturer configures the warning strategy
  • Reduced or disabled antilock braking function, which may only become apparent during hard braking or on slippery surfaces
  • A stored code with no other drivability complaints, so many drivers notice nothing beyond the warning lights
  • In rare cases, a message on the driver information display advising that a brake system service is required

Common causes, most likely first

  1. A failed brake booster temperature sensor B that internally shorts toward a reference voltage or loses its ground reference
  2. Corroded, pushed-back, or damaged terminals at the sensor connector or at the ABS module harness connector
  3. A chafed or shorted signal wire between the sensor and the ABS module, often where the harness passes near hot or moving components
  4. An open or high-resistance ground circuit for the sensor, which biases the signal voltage upward
  5. A faulty ABS control module with an internal driver or analog-to-digital conversion fault on that input channel
  6. Contamination or excessive heat at the sensor mounting location that damages the sensing element
  7. A replacement sensor of the wrong specification or a poor aftermarket connector repair that changes circuit resistance

How to diagnose and fix it

  1. Connect a scan tool and record all ABS and body codes, then clear the code and verify whether C057A returns immediately or only after a drive cycle
  2. Inspect the sensor connector and the ABS module connector for corrosion, bent pins, and loose terminal tension, repairing terminals as needed
  3. Measure resistance across the sensor B terminals and compare with the manufacturer's specification for the current temperature
  4. Back-probe the signal circuit at the ABS module and compare the voltage with the sensor output to determine whether the fault is in the wiring or the module
  5. Load-test the sensor ground circuit with a test light or a voltage drop measurement to rule out a high-resistance ground
  6. Check the harness routing for chafing, heat damage, or pinching near the booster and repair the affected section with a proper splice
  7. If the wiring and sensor both test good, substitute a known-good sensor or module only after confirming the signal voltage is out of range at the module pin

What the booster temperature sensor really does

  • The brake booster temperature sensor exists to protect the booster and nearby components from heat damage, so a high circuit code can be set by a genuine overheating condition rather than an electrical fault.
  • A poor ground at the sensor can raise the signal voltage just enough to set C057A without any visible wiring damage, which is why a voltage drop test on the ground side is essential.
  • Technicians sometimes replace the ABS module when the real fault is a chafed signal wire that only shorts when the engine moves under load, so wiggle-testing the harness while watching live data is a key step.
  • This code can appear after a booster or master cylinder replacement if the sensor connector is not fully seated or the sensor is disturbed during the repair.
  • On some vehicles the same sensor input is shared with other temperature protection strategies, so a high reading can also inhibit certain stability control functions even when base braking feels normal.

Can I keep driving with C057A?

The vehicle remains drivable with normal base braking in most cases, but antilock and stability control functions may be disabled, so avoid hard braking and slippery conditions until the fault is repaired. If the brake pedal feel changes or a red brake warning light appears, stop driving and have the vehicle inspected immediately.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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