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P codepowertrainMedium severity

P057ABrake Pedal Position Sensor "A" Circuit

A general electrical fault has been detected in the brake pedal position sensor circuit.

Definition

The brake pedal position (BPP) sensor gives the PCM and brake control modules a continuous measurement of pedal travel, used for brake-override, cruise/adaptive-cruise disengagement, push-button start authorization, and on hybrids for regenerative brake blending. P057A sets when the sensor's signal, supply, or ground circuit shows an electrical fault that does not fit a more specific low/high code. Symptoms can include a no-start with push-button ignition, cruise control disabled, brake lights misbehaving, and on hybrids reduced regenerative braking with warning lamps. Because the sensor feeds brake-related safety strategies, this code deserves prompt attention.

Common causes

  • Faulty brake pedal position sensor
  • Damaged or corroded wiring/connector at the sensor
  • Open or shorted 5 V reference or ground circuit shared with other sensors
  • Misadjusted or loose sensor mounting after brake pedal or booster service
  • Water intrusion in the connector under the dash or in the pedal area
  • Faulty control module input (rare)

Common misdiagnoses

  • Replacing the brake light switch when the position sensor is a separate component
  • Replacing the ABS module
  • Replacing the push-button start switch for the resulting no-start complaint
  • Replacing the brake master cylinder or booster

Troubleshooting steps

  1. 1.View the BPP sensor PID on a scan tool

    Watch pedal position while slowly pressing the pedal; the value should sweep smoothly from rest to full travel with no dropouts.

  2. 2.Verify sensor supply and ground

    Check for a solid 5 V reference and less than 0.1 V drop on the ground circuit at the sensor connector with the key on.

  3. 3.Measure the signal voltage through pedal travel

    Back-probe the signal wire and confirm a smooth analog sweep (typically roughly 0.5-4.5 V) without dead spots or spikes.

  4. 4.Inspect wiring and the connector

    Look for chafing where the harness flexes near the pedal assembly and for corrosion or backed-out terminals in the connector.

  5. 5.Check sensor mounting and adjustment

    Confirm the sensor is seated and indexed correctly on the pedal assembly, especially after any recent brake or dash work.

  6. 6.Replace and relearn if required

    If the sensor fails testing, replace it and perform any scan-tool zero-point or pedal-position relearn the manufacturer specifies.

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