P057B
Brake Pedal Position Sensor A Circuit Range/Performance.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 5
- AreaVehicle speed, idle control and auxiliary inputs
- 7B
- FaultThe specific fault in that area
What it means
P057B is the generic code for a range or performance fault in the brake pedal position sensor 'A' circuit. The control unit compares the brake pedal position signal with other inputs, such as the brake light switch, brake pressure or vehicle speed, and has seen a signal that does not make sense or does not match. The exact sensor type and which inputs are compared depend on the make and model.
Symptoms
- Warning light on the dashboard (engine management light, and possibly brake or stability control warnings)
- Brake lights staying on, not coming on, or working intermittently
- Cruise control or adaptive cruise control unavailable
- Engine or gearbox going into a reduced-performance mode on some vehicles
- Hesitant starting or stop-start system not working on vehicles where the brake pedal signal is needed
- Erratic or unexpected regenerative braking feel on hybrid and electric vehicles
Possible causes
- Faulty or worn brake pedal position sensorlikely
- Brake pedal sensor or brake light switch out of adjustment, or mounting loose or damagedlikely
- Wiring damage, chafing, corrosion or poor connector contact in the sensor circuitlikely
- Poor or incorrect reference voltage or earth supply to the sensorpossible
- Mechanical problem at the pedal, such as a bent bracket, a worn pedal bush or an obstruction under the pedalpossible
- Fault in the control unit or in a related brake module that compares the signalsrare
How to diagnose
- Read all stored and pending codes and the freeze frame data, and note any related brake, stability control or brake light switch codes.
- Check the brake lights work properly when the pedal is pressed and released, and look for anything under the pedal that could interfere with its movement.
- Inspect the sensor, its mounting and the pedal linkage for looseness, damage or incorrect adjustment, following the procedure for the specific model.
- Inspect the wiring and connector for chafing, corrosion, water ingress, bent pins and poor terminal tension.
- With a scan tool, watch the live brake pedal position and brake switch values while pressing the pedal slowly, and look for dropouts, jumps or a signal that does not follow the pedal travel.
- Check the sensor supply voltage, signal and earth against the manufacturer's specification, as the sensor type and values vary by model.
- Check battery condition and charging voltage, as low voltage can upset sensor readings and cause false faults.
- Check for software updates or technical bulletins for the vehicle only if the wiring and sensor test fine.
How to fix
- Replace the brake pedal position sensor and set or calibrate it as the manufacturer specifies.
- Re-adjust or refit the sensor and brake light switch, and repair or replace any damaged mounting or pedal parts.
- Repair damaged wiring, and clean or replace corroded or faulty connectors.
- Restore a correct supply voltage or earth connection to the sensor circuit.
- Replace or reprogram the affected control unit only after the other causes are ruled out, and only if the manufacturer's procedure calls for it.
- Clear the code and road test to confirm that it does not return.
Can I keep driving?
The car can usually be driven carefully for a short time, but get it checked soon. If the brake lights are not working properly, or the brake warning lights are on, avoid driving it until it is fixed, as it is unsafe for other road users.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.