Brake switch out of adjustment, worn or failed internally; Faulty or misaligned brake pedal switch plunger, or a missing or damaged pedal stopper or bump pad; Damaged wiring, corrosion or loose connector at the brake switch; Blown brake light fuse or failed brake light circuit; Open or short circuit in the wiring between the switch and the control unit; Faulty body control module or other module that shares the brake switch signal; Fault in the engine control unit input circuit.

P0571

Brake Switch A Circuit.

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
71: FaultThe specific fault in that area

What it means

P0571 is the generic SAE J2012 code for a fault in the Brake Switch A circuit. The engine control unit monitors the brake pedal switch signal, which is used for cruise control cancellation and to confirm brake application. It sets the code when the signal is implausible, stuck, missing, or disagrees with other inputs such as vehicle speed or a second brake switch signal. The exact logic varies by manufacturer and model.

Symptoms

Cruise control not working or cancelling unexpectedly
Brake lights not working, staying on, or flickering
Engine management warning light on
Difficulty starting or shifting out of park on some models
Reduced or altered idle or throttle response on some models
Adaptive cruise or stop-start system disabled

Possible causes

Brake switch out of adjustment, worn or failed internallylikely
Faulty or misaligned brake pedal switch plunger, or a missing or damaged pedal stopper or bump padlikely
Damaged wiring, corrosion or loose connector at the brake switchlikely
Blown brake light fuse or failed brake light circuitpossible
Open or short circuit in the wiring between the switch and the control unitpossible
Faulty body control module or other module that shares the brake switch signalrare
Fault in the engine control unit input circuitrare

How to diagnose

Read the stored codes and freeze frame data, and note any other brake, cruise or body control codes present.
Check that the brake lights work and switch off when the pedal is released, and confirm that all bulbs and the relevant fuse are good.
Visually inspect the brake switch, its mounting and the pedal stopper for damage, misalignment or wear.
Inspect the switch connector and wiring for corrosion, bent pins, chafing and water ingress.
With a scan tool, watch the live brake switch status while pressing and releasing the pedal and check that it changes cleanly and promptly.
Measure the switch supply, signal and earth with a multimeter, following the manufacturer's wiring diagram for the model, and check the switch resistance or continuity through its travel.
Check the wiring between the switch and the control unit for open circuits, shorts and high resistance.
If the switch and wiring are sound, check the control unit input and any shared modules following manufacturer procedures.

How to fix

Adjust or replace the brake pedal switch as specified for the model.
Replace a damaged pedal stopper or bump pad and correct the switch alignment.
Repair damaged wiring and clean or replace corroded or damaged connector terminals.
Replace blown fuses after finding the cause, and repair the brake light circuit fault.
Repair or replace a faulty control unit or shared module only after the inputs and wiring have been proven good.

Can I keep driving?

Medium severity

The car can usually be driven short-term, but faulty brake lights are a safety and legal concern, so check them straight away. Get it repaired soon, as cruise control and some other functions may be unavailable until it is fixed.

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