Damaged, chafed or broken wiring to the brake pedal sensor B circuit; Corroded, loose or pushed-out pins in the sensor connector; Faulty brake pedal position sensor B (internal open circuit); Sensor reference voltage or ground supply missing or faulty; Sensor misaligned or incorrectly fitted after pedal or brake light switch work; Fault inside the control unit that reads the sensor.

P05DB

Brake Pedal Position Sensor B Circuit/Open.

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
DB: FaultThe specific fault in that area

What it means

P05DB means the control unit has detected an open circuit, or no valid signal, on the brake pedal position sensor B circuit. The sensor's signal, reference or ground connection is not reaching the control unit as expected, so the signal sits outside its normal range. The exact wiring layout, and which systems use sensor B, depends on the make and model.

Symptoms

Warning light on the dashboard, such as the engine or brake system warning
Brake lights not working, or staying on all the time
Cruise control or adaptive cruise control unavailable
Reduced engine power or limited response in some vehicles
Stop-start disabled or the engine hard to start or stop on push-button cars
Other stability or brake system fault codes stored alongside

Possible causes

Damaged, chafed or broken wiring to the brake pedal sensor B circuitlikely
Corroded, loose or pushed-out pins in the sensor connectorlikely
Faulty brake pedal position sensor B (internal open circuit)likely
Sensor reference voltage or ground supply missing or faultypossible
Sensor misaligned or incorrectly fitted after pedal or brake light switch workpossible
Fault inside the control unit that reads the sensorrare

How to diagnose

Read the freeze frame data and all stored codes, noting any related brake, cruise or stability faults, then check for any technical service information for the model.
Check the brake lights work correctly, both when the pedal is pressed and when it is released.
Visually inspect the sensor, connector and wiring near the pedal for damage, rubbing, water ingress or corrosion.
Check the live data for the brake pedal sensors and compare sensor A and B as the pedal is pressed and released slowly.
Wiggle test the harness and connector while watching live data for dropouts.
With the connector unplugged, check the reference voltage and ground supply at the sensor against the manufacturer's data.
Check the signal wire for continuity, and for shorts to ground or voltage, back to the control unit.
Check the sensor mounting and adjustment against the manufacturer's procedure, then clear the code and retest.

How to fix

Repair or replace the damaged wiring section, using proper soldered and sealed repairs or a new harness section.
Clean, repair or replace the corroded or damaged connector terminals.
Replace the brake pedal position sensor B if it fails the electrical tests, and set it up as the manufacturer specifies.
Restore the missing reference or ground supply by repairing the wiring or the faulty supply.
Refit and adjust the sensor correctly if it is loose or misaligned.
Diagnose and, if confirmed faulty, replace or repair the control unit as a last resort.

Can I keep driving?

Medium severity

Check first that the brake lights work properly. If they do not, or the car loses power or the brakes feel abnormal, do not drive it. Otherwise it can be driven carefully to a workshop, but get it fixed soon.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.