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DTC codes / P05xx · Vehicle speed, idle control and auxiliary inputs / P05DB

P05DBBrake Pedal Position Sensor B Circuit/Open

P05DB means the powertrain control module (PCM) has detected an open circuit on the signal or return path of brake pedal position sensor B, which is the second of two redundant brake pedal sensors on many modern vehicles. The PCM monitors expected voltage on that circuit and flags the code when the signal falls outside the plausible range for a calibrated period, indicating a broken wire, poor connection, or failed sensor.

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 with no other noticeable symptoms
  • Extended cranking or a no-crank condition because the PCM cannot confirm the brake pedal is depressed for push-button start
  • Inability to shift the transmission out of Park, since the brake pedal signal is required for the shift interlock
  • Cruise control refusing to engage or disengaging unexpectedly when the brake pedal is touched
  • Reduced or disabled regenerative braking on hybrid and electric vehicles that rely on brake pedal position for blending
  • A stored code with a freeze-frame showing the fault occurred during a brake pedal application or at a specific vehicle speed

Common causes, most likely first

  1. Broken, chafed, or corroded wiring in the brake pedal position sensor B signal or return circuit, especially near the pedal assembly or through the firewall
  2. Loose, backed-out, or corroded terminals at the sensor connector or at the PCM connector
  3. Failed brake pedal position sensor B itself, typically due to internal wear of the potentiometer or hall-effect element
  4. Water intrusion or contamination in the sensor connector causing an intermittent open circuit
  5. A faulty or misadjusted brake pedal assembly that prevents sensor B from sweeping through its expected range
  6. Damage to the sensor pigtail from pedal travel, debris, or previous service work in the footwell
  7. Rarely, an internal open circuit in the PCM driver for that sensor input

How to diagnose and fix it

  1. Connect a scan tool and record all stored codes, freeze-frame data, and live brake pedal position sensor B voltage while slowly pressing and releasing the pedal to confirm the open circuit
  2. Visually inspect the sensor B connector, pigtail, and wiring harness for chafing, corrosion, water intrusion, or loose terminals, and repair any obvious damage
  3. Backprobe the sensor B signal and return wires at the connector and measure resistance or voltage drop while wiggling the harness to expose an intermittent open
  4. Check continuity from the sensor connector to the PCM connector on both the signal and return circuits, repairing any open or high-resistance wire
  5. If wiring and connectors pass, replace brake pedal position sensor B with a quality part and clear the codes
  6. Relearn or calibrate the brake pedal position sensors using the scan tool procedure required by the manufacturer, then verify live data tracks smoothly through the full pedal travel
  7. Clear all codes, perform a road test that includes braking, cruise control engagement, and shift interlock operation, and confirm the code does not return

Why brake pedal sensor B fails when sensor A is fine

  • Many vehicles use two brake pedal position sensors that must agree within a small tolerance, so a perfectly working sensor A can mask a failing sensor B until the PCM compares the two signals and sets P05DB.
  • A common misdiagnosis is replacing the brake pedal position sensor when the real fault is a chafed wire in the footwell or a corroded connector pin that only opens when the pedal is pressed or the harness flexes.
  • On vehicles with push-button start, an open on sensor B can prevent the engine from cranking even though the brake lights work normally, because the PCM uses the redundant sensor for start authorization.
  • After replacing the sensor, many manufacturers require a calibration or relearn procedure; skipping it can leave the code stored or cause poor brake pedal feel and improper cruise control operation.
  • A weak or failing battery can cause voltage spikes that set communication or sensor codes, so always verify battery health and charging system output before condemning the sensor circuit.

Can I keep driving with P05DB?

The vehicle is generally safe to drive to a repair shop because the primary brake pedal sensor and hydraulic brakes remain functional, but avoid relying on cruise control and be aware that push-button start or shift interlock may act up. If the brake warning light is on along with ABS or stability control warnings, keep speeds low and get the fault diagnosed promptly.

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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