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DTC codes / P05xx · Vehicle speed, idle control and auxiliary inputs / P057C

P057CBrake Pedal Position Sensor A Circuit Low

P057C indicates that the powertrain control module (PCM) has detected a low voltage condition on the signal circuit of brake pedal position sensor A. The sensor normally outputs a voltage that rises as the brake pedal is pressed, and the PCM sets this code when the signal stays below the expected minimum for the current pedal state.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • Illumination of the brake system warning light, ABS light, or check engine light
  • Often no symptoms besides the warning light, especially if the brake lights still work
  • Brake lights may stay on continuously or fail to illuminate when the pedal is pressed
  • Cruise control may not engage or may disengage unexpectedly
  • Rough or delayed transmission shifts, particularly when coming to a stop
  • Extended crank or no-start condition if the PCM relies on the brake pedal signal for starting logic

Common causes, most likely first

  1. Faulty brake pedal position sensor A (internal short to ground or open circuit)
  2. Damaged or corroded wiring harness between the sensor and the PCM
  3. Loose or contaminated electrical connector at the sensor
  4. Blown fuse or poor ground connection serving the sensor circuit
  5. Brake pedal linkage misalignment or binding that prevents the sensor from moving through its full range
  6. Water intrusion or debris in the sensor connector causing a short to ground
  7. PCM internal fault (rare, but possible after other causes are ruled out)

How to diagnose and fix it

  1. Use an OBD-II scan tool to read all stored codes and freeze-frame data, then clear codes and verify whether P057C returns
  2. Visually inspect the brake pedal position sensor, its connector, and the wiring harness for damage, corrosion, or loose pins
  3. Measure reference voltage and ground at the sensor connector with a digital multimeter with the key on and engine off
  4. Back-probe the signal wire and observe voltage as the brake pedal is slowly pressed and released, comparing to the manufacturer's specification
  5. Check the sensor's resistance or voltage output across its full travel and replace the sensor if it does not change smoothly or stays out of range
  6. Repair any damaged wiring, replace corroded terminals, and ensure the connector locks securely
  7. After repairs, clear codes, perform a road test with several brake applications, and confirm the code does not reset

Why a brake pedal sensor code is not always the sensor

  • A low signal voltage often comes from a short to ground in the wiring, not from a failed sensor, so a sensor replacement without circuit testing can be wasted money.
  • The brake pedal position sensor is frequently confused with the brake light switch, but they are separate components on many vehicles and only one may be faulty.
  • A misadjusted or binding brake pedal linkage can hold the sensor at the low end of its travel and set P057C even though the sensor itself is good.
  • Water or road salt intrusion into the connector can create a partial short that only appears in damp weather, making the code intermittent and hard to reproduce.
  • Some vehicles use the brake pedal position signal for cruise control and transmission logic, so a low signal can cause drivability complaints that seem unrelated to the brakes.

Can I keep driving with P057C?

The vehicle is generally safe to drive if the brake lights work and the pedal feels normal, but avoid long trips and towing until the fault is repaired. If the brake lights stay on continuously or the pedal feels abnormal, stop driving and have the system inspected immediately.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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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