BrakesGeneric OBD-II codeUrgency: Garage soon
Code P0571: cruise control brake switch (circuit A)
P0571 means: cruise control/brake switch "A" circuit malfunction.[1][2] The engine ECU has detected a fault in brake switch circuit "A", the one that tells it the pedal is being pressed. That signal is used to cancel cruise control when you brake, and the same switch also plays a part in the brake lights and, on automatic gearboxes, in the interlock that lets you move the lever out of P.[1][2][3]
What code P0571 means
The engine ECU has detected a fault in brake switch circuit "A", the one that tells it the pedal is being pressed. That signal is used to cancel cruise control when you brake, and the same switch also plays a part in the brake lights and, on automatic gearboxes, in the interlock that lets you move the lever out of P.[1][2][3]
CarParts.com warns that the "A" may refer to a specific wire, connector or harness, and that the exact definition depends on the manufacturer's manual. In the 2008 Saab 9-3 workshop manual, code P0571 appears as "incorrect signal from the brake light switch circuit" and the system's reaction is to disable cruise control.[3][4]
It is a generic OBD-II code (it starts with P0), so it means the same on any make, although the repair procedure varies by manufacturer and model.[1][2][5]
Original definition (SAE J2012): Cruise Control/Brake Switch A Circuit Malfunction[1][2]
Causes of P0571
From most to least likely, according to the sources.
- 1Faulty brake light switch (or cruise control/brake switch).[1][3]
- 2Damaged switch wiring, a short circuit in the signal wire, or corroded or loose connectors.[1][3][4]
- 3Switch incorrectly adjusted on the brake pedal.[1]
- 4Blown fuse in the brake light circuit.[1]
- 5Mechanical problems with the brake pedal.[1]
- 6Faulty engine ECU (ECU/PCM).[1][3]
Symptoms
- Cruise control will not engage, works erratically or switches off unexpectedly.[1][3][4]
- Brake lights that may not come on when you brake or, according to Autodoc Club, stay on permanently.[1][3]
- On automatic gearboxes, problems changing gear or moving the lever out of P, because the brake switch is involved in that interlock.[1][3]
- Engine warning light permanently on.[1][3]Engine warning light: faults that cause it
How to diagnose P0571
In order: from the most likely and cheapest to check to the most expensive.
- 1Check whether the brake lights come on when you press the pedal and go off when you release it, and whether cruise control engages: it is the quickest and cheapest test.[1][3]
- 2With a diagnostic tool, watch the brake light switch signal (and that of the pedal switch, if the car has two) while you press and release the brake.[3][4]
- 3Check the brake light circuit fuse in the fuse box.[1]
- 4Inspect the switch connector and wiring: corrosion, loose contacts, damaged or short-circuited wires. Clean the connectors with contact cleaner spray and reconnect them firmly.[1][4]
- 5Check that the switch is adjusted on the pedal to the manufacturer's specifications and that the pedal has no mechanical problems.[1]
- 6Replace the switch only if the tests confirm it, with a new one of the correct part number, and adjust it properly on the pedal.[1][3]
- 7Procedures vary by make and model: consult the manufacturer's manual or a repair database before working on it, and leave complex diagnoses and ECU problems to a garage.[1][3]
- 8Only if everything above checks out, consider an engine ECU fault.[1]
Can I keep driving with P0571?
Garage soon
You can keep driving, but the sources warn of a safety risk. Autodoc Club speaks of a "considerable risk" because cruise control is out of action and the brake lights may not work properly, and recommends repairing it as soon as possible. CarParts.com adds that a faulty switch can leave you without brake lights and increase the risk of an accident, and TaT points out that, if the circuit fails, cruise control might not cancel when you brake. To be safe, check that the brake lights work and avoid using cruise control until it is repaired.[1][2][3]
Documented faults related to P0571
Known faults of specific engines and cars, with their repair cost, the affected years and their sources.
Brake pedal, hoses and brake fluid: the most serious faults by engine and car
- Critical severityFrequency: Very frequentOpel Corsa FBrake fluid leak and loss of ABS/ESP from the EBS valve block (2024 production)The manufacturer recalled Opel Corsa F cars built between 24 May and 27 August 2024 because of an EBS valve block with a casting defect that can cause an internal brake fluid leak and the loss of stability control, ABS and electronic brake distribution.
- Critical severityFrequency: Very frequentPeugeot 208 IIBrake fluid leak and loss of ABS/ESP due to the EBS valve block (2024 production)The manufacturer recalled Peugeot 208 IIs built between 27 May and 6 June 2024 over an EBS valve block with a casting defect that can cause an internal brake fluid leak and loss of ABS and ESP. The Opel Corsa has an equivalent campaign with different dates.
- Critical severityFrequency: CommonMercedes-Benz Clase E W211SBC (Sensotronic Brake Control) electrohydraulic braking system failuresThe E-Class W211 introduced the SBC electrohydraulic braking system, which could fail because of a faulty control of its high-pressure pump, especially in extreme situations; Mercedes-Benz recalled it twice (2004 and 2005) and ended up removing it completely in the 2006-2007 facelift after customer complaints.Appears at around 120,000 km
- Critical severityFrequency: CommonOpel Astra KBrake master cylinder contaminated by clutch debrisYes: Opel recalled 2016-2018 Astra K cars because the seal on the clutch slave cylinder can release particles that contaminate the brake master cylinder, lengthen the pedal travel and reduce braking power.
Headlights and lights: the most serious faults by engine and car
- High severityFrequency: CommonPeugeot 307Exterior light failure without warning (2006-2009 production)On cars built between 2006 and 2009, the exterior lights can go out or fail without warning; Peugeot issued two recalls for this reason, and gebrauchtwagenberater.de independently documents a lighting problem on models from those years.
- Critical severityFrequency: OccasionalAlfa Romeo TonaleFaulty wiring under the floor: loss of lights, power steering and brake servo (Tonale 2022-2023)Yes: a Safety Gate alert from March 2023 (campaign 6574) covers 607 Tonales built between 15 September 2022 and 13 February 2023, whose wiring under the floor can knock out the lights, hazard lights, power steering and brake servo.
- High severityFrequency: OccasionalCitroën C-CrosserOut-of-specification electronic component in the built-in systems interface (BSI): lights, wipers and sat nav may failYes: an electronic component in the Citroën C-Crosser's built-in systems interface (BSI) may not meet the specification and cause the audio-navigation, the wipers and the exterior lighting to fail, with a warning light on the dashboard. The DVSA states that the BSI's build date is checked and the unit is replaced if it falls in the affected range.
- High severityFrequency: OccasionalCitroën C-CrosserBrake light switch with contacts contaminated by silicone greaseYes: in 2014 a campaign was registered because the brake light switch on the C-Crosser, built between April 2007 and June 2009, could have its contacts contaminated with silicone grease from the factory, and the brake lights might not come on when the pedal is pressed. The switch is replaced and its wiring harness cleaned.
Wiring, connectors and short circuits: the most serious faults by engine and car
- Critical severityFrequency: OccasionalBMW N62 / N63Additional turbo coolant pump with a risk of short circuit and fireIn 2011 BMW recalled 5, 6 and 7 Series, X5 and X6 models built between 2007 and 2011 because of the additional turbo coolant pump: moisture, a short circuit and, in extreme cases, a fire. In 2012 there was another campaign for a crack in the pump, with a more robust version.
- High severityFrequency: Occasional1.3 TCeBlown fuel pump fuseOn the Renault Captur II and Clio V with the 1.3 TCe engine, a 20-amp fuse can blow and leave the car without an engine. According to L'argus, in April 2021 this fault still had no factory fix; the official service centre's diagnosis includes checking, and sometimes replacing, the catalytic converter.
- High severityFrequency: OccasionalM264/M254Poorly tightened 48 V earth wiring in the mild-hybrid system (fire risk)Mercedes-Benz has issued several recalls (2022-2025) because the 12 V and 48 V earth connections of some cars with a 48 V system may be poorly tightened: resistance rises, the connection heats up and a fire cannot be ruled out. The official workshop checks them and repairs them if necessary in an hour or more.
- High severityFrequency: Occasional1.9 TDIUnit injector tappet wear and injector wiring damageOn the unit injector system, the tappets that operate the injectors can wear if the oil is not changed on time, and the injector wiring can be damaged by contact with oil, causing misfires or loss of power.
- Critical severityFrequency: CommonRover 75Seat SRS connector fault with airbag and seatbelt warning light onAuto Express warns that the Rover 75's seat SRS connector can cause the airbags to fail, and dealers were fixing it with revised connectors. The Dutch APK inspection puts the airbag or seatbelt fault warning among the most frequent defects across almost all series.
- Critical severityFrequency: OccasionalAlfa Romeo GiuliettaShort circuit from badly routed wiring that can prevent gear shifting (KBA campaign, 2010-2015)Yes: according to Germany's KBA, on Alfa Romeo Giulietta cars built between 2010 and 2015 inadequate cable routing could cause a short circuit and, as a result, gear-shift failure.
Driver assistance and automatic emergency braking: the most serious faults by engine and car
- Critical severityFrequency: Very frequentToyota Auris IIThe Takata driver's airbag inflator can degrade and fragment when deployedOn units built between 2006 and 2017, the propellant in the Takata inflator of the driver's airbag can degrade over time and with humidity; if the airbag deploys, the inflator can rupture and throw metal fragments at the occupants. Toyota fixes it by replacing the inflator free of charge at the official dealer.
- Critical severityFrequency: OccasionalMazda 3 IVSmart Brake Support can brake the car unintentionally while drivingOn cars built between November 2018 and October 2019, an unintended activation of the Smart Brake Support automatic braking system can stop the car unexpectedly while it is moving, with a risk of the vehicle behind running into it. Mazda inspects it free of charge at an official dealer.
- Critical severityFrequency: OccasionalMazda CX-30Smart Brake Support can brake the car unintentionally while drivingOn cars built between November 2018 and October 2019, an unintended activation of the Smart Brake Support automatic braking system can stop the car unexpectedly while it is moving, with a risk of the vehicle behind running into it. Mazda inspects it free of charge at an authorised dealer.
- Critical severityFrequency: OccasionalToyota C-HR IThe pre-collision system radar can fail without warning the driverOn vehicles built between 2020 and 2021, a faulty radar sensor installation can stop the pre-collision system (PCS) from detecting a vehicle ahead, with no warning or assisted braking and no message that the system is not working. Toyota fixes it by inspecting the radar at an official service centre.
Frequently asked questions
Why does code P0571 leave me without cruise control?
Because the brake switch is the signal the ECU uses to know you have pressed the pedal and to cancel cruise control, and the sources note that, when the circuit fails, cruise control cannot be engaged or switches off. The 2008 Saab 9-3 workshop manual documents that system reaction: cruise control disabled.[1][2][3][4]
Can I drive with code P0571?
You can, but with caution and by repairing it as soon as possible. Autodoc Club speaks of a considerable safety risk, because the brake lights may not work properly and cruise control is out of action; CarParts.com reminds us that without brake lights the risk of an accident increases.[1][3]
Why can a brake switch fault affect the automatic gearbox?
Because the brake switch is also involved in the interlock that requires you to press the brake to move the lever out of P. Autodoc Club lists gearbox problems among the symptoms, and CarParts.com includes that interlock among the functions of the brake switch.[1][3]
Can I repair P0571 myself?
Simple tasks such as cleaning the connectors or replacing the brake light switch are within reach of an experienced DIYer, according to Autodoc Club. More complex diagnoses and ECU problems are best left to a garage, and CarParts.com recommends following the specific manual for each vehicle.[1][3]
Does P0571 mean the same on all makes?
Yes. It is a generic OBD-II code (it starts with P0) and can appear on any OBD-equipped vehicle. What varies from one make to another is the diagnostic and repair procedure.[1][2][5]
Will I pass the MOT with code P0571?
If the code has switched on the engine warning light, no: with that light on, the inspection records a serious defect, and on Euro 5 and Euro 6 cars the ITV (Spain's roadworthiness inspection, similar to the MOT) also reads the OBD diagnostic system. Repair the fault before you go; clearing the code just before the inspection does not help either, because it counts as a serious defect.[6]
Not sure what is wrong with your car? Describe what you notice in the symptom diagnosis or see all fault codes.
Sources
Every fact on this page links to its source. If you find an error, let us know.
- Código de avería P0571 - guía paso a paso para su diagnóstico y resoluciónAutodoc Club · Technical documentation · consulted 2 October 2026 · in Spanish
- P0571 — Cruise Control/Brake Switch A Circuit MalfunctionThe Automotive Technician (TaT) · Technical documentation · consulted 2 October 2026
- P0571 Code: Cruise Control / Brake Switch A Circuit MalfunctionCarParts.com · Technical documentation · published 19 December 2024 · consulted 2 October 2026
- DTC P0571 01: Brake-Light Switch Circuit Incorrect Signal (Saab 9-3, 2008)SAAB WIS Online (copia del manual de taller de Saab) · Technical documentation · consulted 2 October 2026
- On-board diagnosticsWikipedia · Other source · consulted 2 October 2026
- Desmontando mitos: ¿puede pasar mi coche la ITV con el testigo de «avería motor» encendido?Diariomotor · Motoring press · published 8 March 2021 · consulted 2 October 2026 · in Spanish