Faulty brake pedal position sensor B or its internal circuit; Wiring short to ground or chafed insulation in the sensor B signal circuit; Corroded, loose or damaged connector terminals at the sensor or control unit; Open circuit or poor connection in the sensor's reference supply, leaving the signal low; Sensor incorrectly adjusted, loose or displaced after pedal or brake switch work; Fault in the control unit's sensor supply or input circuit.

P05DD

Brake Pedal Position Sensor B Circuit Low.

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
DD: FaultThe specific fault in that area

What it means

P05DD means the engine or powertrain control unit has seen the signal voltage from brake pedal position sensor B fall below the expected range. The sensor circuit is monitored for its voltage while the pedal is at rest and while it moves. A reading that sits too low points to a short to ground, a wiring or supply fault, or a failed sensor. Sensor location and how many sensors are fitted vary by model.

Symptoms

Engine management light on
Brake lights not working, or staying on
Cruise control or speed limiter unavailable
Reduced engine power or limited response in some models
Stop-start system disabled
Other brake-related or stability control warnings in some models

Possible causes

Faulty brake pedal position sensor B or its internal circuitlikely
Wiring short to ground or chafed insulation in the sensor B signal circuitlikely
Corroded, loose or damaged connector terminals at the sensor or control unitlikely
Open circuit or poor connection in the sensor's reference supply, leaving the signal lowpossible
Sensor incorrectly adjusted, loose or displaced after pedal or brake switch workpossible
Fault in the control unit's sensor supply or input circuitrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, then check for related brake, stability control or reference voltage codes.
Check that the brake lights come on and go off correctly with the pedal, as this indicates whether the brake signal is being received.
Inspect the sensor, connector and wiring near the pedal box for damage, water ingress, corrosion, chafing or poor pin tension.
View live data for brake pedal position sensors A and B while pressing and releasing the pedal slowly, and look for a low, flat or erratic B signal against A.
With the connector unplugged and ignition on, check the reference supply and ground at the sensor against the manufacturer's wiring data for that model.
With the ignition off and the control unit disconnected as the data directs, test the signal wire for a short to ground and for continuity and resistance.
Check the sensor mounting and adjustment, and the pedal for free movement, following the procedure for that model.
If the wiring and supply are proven good, test or substitute the sensor, and only then suspect the control unit.

How to fix

Replace the brake pedal position sensor if it fails the live data or electrical tests, and adjust it as the model requires.
Repair or replace the damaged section of wiring causing the short to ground or open circuit.
Clean, repair or replace faulty connector terminals and reseat the connector securely.
Restore the reference supply or ground connection if that is found to be faulty.
Refit or adjust the sensor correctly and carry out any required calibration or learning procedure for the model.
Repair or replace the control unit only if a confirmed internal fault is found.

Can I keep driving?

Medium severity

Check the brake lights first. If they work normally, the car can be driven carefully for a short time until it is repaired. If they do not work, or stay on, or the car is in limp mode, avoid driving until it is fixed.

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