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P codepowertrainMedium severity

P057BBrake Pedal Position Sensor "A" Circuit Range/Performance

The brake pedal position sensor signal is implausible compared with expected values or with other brake inputs.

Definition

The PCM continuously rationality-checks the brake pedal position sensor against the brake light switch, a redundant second sensor track, or expected pedal behavior — for example, the sensor should read near zero at rest and agree with the switch when the pedal is pressed. P057B sets when the signal is in range electrically but does not make sense, such as indicating pedal travel with the brake switch open. Consequences include disabled cruise and adaptive cruise, possible brake-override intervention limiting throttle, push-button start problems, and reduced regenerative braking on hybrids.

Common causes

  • Drifted or internally worn brake pedal position sensor
  • Misadjusted sensor or brake light switch causing the two inputs to disagree
  • Worn pedal pivot bushings changing the sensor's rest position
  • High resistance in the sensor circuit skewing the reading
  • Zero-point calibration lost or never performed after component replacement
  • Intermittent wiring fault at the pedal-area connector

Common misdiagnoses

  • Replacing the brake pedal position sensor when only a relearn/calibration was needed
  • Replacing the brake light switch without checking its adjustment
  • Replacing the ABS module
  • Replacing the accelerator pedal sensor for brake-override throttle limiting

Troubleshooting steps

  1. 1.Compare BPP sensor and brake switch PIDs

    Press the pedal slowly and confirm the sensor sweeps in step with the switch state change; note the exact point of disagreement.

  2. 2.Check the sensor's rest reading

    With the pedal fully released, the position value should be at or very near the calibrated zero point; an offset suggests drift or mechanical wear.

  3. 3.Perform the zero-point calibration

    Run the manufacturer's pedal position relearn with a scan tool and see whether the rationality fault clears.

  4. 4.Inspect pedal hardware and switch adjustment

    Check for worn pedal bushings, a missing switch stop pad, and correct brake light switch plunger clearance.

  5. 5.Test circuit integrity under load

    Voltage-drop test the sensor supply, ground, and signal circuits; more than 0.1 V of unexplained drop can skew an otherwise in-range signal.

  6. 6.Replace the sensor if drift is confirmed

    Fit a new sensor, recalibrate, and verify sensor and switch agree through several full pedal applications.

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