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DTC codes / C05xx · Brakes, steering and suspension / C057B

C057BBrake Booster Temperature Sensor B Circuit/Open

C057B indicates that the antilock braking system (ABS) control module has detected an open circuit or excessive resistance in the signal circuit for the brake booster temperature sensor B. This sensor monitors the temperature of the brake booster, and the module uses that data to protect braking performance; when the circuit is open, the module cannot read the sensor and stores this code.

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

Symptoms you may notice

  • Illumination of the ABS warning light and possibly the traction control light
  • A stored code C057B in the ABS module with no other noticeable symptoms
  • Reduced or disabled ABS and traction control functions
  • In some cases, a soft or inconsistent brake pedal feel
  • Intermittent warning light activation over bumps or during temperature changes
  • No driver-perceptible change in braking performance under normal conditions

Common causes, most likely first

  1. Broken, chafed, or corroded wiring in the brake booster temperature sensor B circuit
  2. Failed brake booster temperature sensor B
  3. Loose or corroded electrical connector at the sensor or ABS module
  4. Open circuit inside the sensor due to age or heat exposure
  5. Damage to the wiring harness from road debris, heat, or improper routing
  6. Faulty ABS control module (less common)
  7. Water intrusion into the connector or sensor causing an open circuit

How to diagnose and fix it

  1. Use a scan tool to confirm C057B and check for any related codes in the ABS module
  2. Visually inspect the sensor, connector, and wiring for damage, corrosion, or looseness
  3. Disconnect the sensor and measure resistance across its terminals to check for an open circuit
  4. Check continuity and resistance of the signal circuit from the sensor connector to the ABS module
  5. Repair or replace any damaged wiring, terminals, or connectors as needed
  6. If the circuit tests good, replace the brake booster temperature sensor B
  7. Clear the code and verify the repair with a test drive and re-scan

What a brake booster temperature sensor open really means

  • A common misdiagnosis is replacing the ABS module when the actual fault is a simple broken wire near the booster, so always check circuit continuity first.
  • The sensor may test fine at room temperature but open internally when hot, so a resistance check while the engine is warm can reveal an intermittent fault.
  • Corrosion inside the connector pins is a frequent cause that visual inspection alone can miss; a pin drag test and voltage drop test are more reliable.
  • This code can set if the sensor is unplugged during unrelated service work, so check for recent repairs before assuming a failed component.
  • Some vehicles use the same temperature sensor signal for multiple functions, so an open circuit may also affect other systems that rely on booster temperature data.

Can I keep driving with C057B?

The vehicle remains safe to drive under normal conditions because the base braking system is unaffected, but ABS and traction control may be disabled. Avoid hard braking or slippery conditions until the fault is repaired, and have the system diagnosed promptly to restore full safety features.

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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