P0571 — Brake Switch “A” Circuit #

The code description may vary slightly depending on the vehicle manufacturer. Always refer to the OEM (Original Equipment Manufacturer) documentation for your specific vehicle.

Known label variations:

• Brake Switch “A” Circuit Malfunction (Ford, Toyota, Honda, GM)
• Brake Pedal Position/Brake Switch “A” Circuit (Volkswagen, Audi)
• Brake Switch Circuit “A” Range/Performance (Hyundai, Kia)

Summary of the P0571 Code #

The P0571 diagnostic trouble code (DTC) indicates that the vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected an issue with the Brake Switch “A” circuit, which monitors the primary brake pedal switch. This component is essential for informing the vehicle’s computer when the brake pedal is pressed—a critical input for functions like cruise control, automatic transmissions, and brake light operation. If this circuit is faulty, the vehicle may not recognize when you’re braking, potentially disabling certain safety functions. It’s a common code across many makes and models, and while the root cause is usually straightforward, it should not be ignored. Immediate attention is recommended to ensure both the safety and reliability of your vehicle systems.

Frequent Symptoms for Code P0571 #

When the P0571 code is present, you may notice some clear and disruptive symptoms. The most obvious sign is often the malfunction or absence of brake lights—posing a direct safety risk. In addition, electronic systems that rely on precise brake input, such as cruise control, may be disabled or operate erratically. The check engine light will illuminate, and on some vehicles, transmission shifting may be affected. Here’s what drivers and technicians typically observe:

• Brake lights do not operate when pressing the pedal
• Cruise control not engaging or disengaging unexpectedly
• Check Engine Light illuminated
• ABS (Anti-lock Brake System) or traction control warning lights may appear
• Transmission may shift harshly or enter “limp” mode in rare cases

Probable Causes for Code P0571 #

The P0571 code is most often triggered by issues with the brake switch itself or its associated wiring. While the switch is a simple device, its failure can have wide-reaching effects. Electrical faults, connector corrosion, and mechanical misalignment are also common culprits. Here’s a rundown of the most frequent causes, in order of likelihood:

1. Faulty brake pedal switch (internal failure or wear)
2. Wiring problems (open, short, or damaged wires between switch and PCM/ECM)
3. Corroded or loose electrical connectors at the switch or module
4. Misadjusted or misaligned brake switch (improper installation or accidental impact)
5. Faulty PCM/ECM (rare, but possible if other causes are ruled out)

Step-by-Step Diagnosis for Code P0571 #

Diagnosing a P0571 code requires a systematic approach, starting with the most common and accessible issues, before moving toward more complex faults. Always prioritize safety—ensure the vehicle is secure and that you have access to basic hand tools and a digital multimeter. Here’s a proven workflow:

• Verify the code with a scan tool, and note any related DTCs (especially ABS or cruise control codes).
• Check brake lights: With ignition ON, press the brake pedal and confirm if the brake lights activate.
• Inspect the brake switch: Locate the switch at the top of the brake pedal assembly. Check for obvious signs of damage or disconnection.
• Test the switch mechanically: Press and release the pedal while observing the switch’s action; ensure it moves freely and clicks.
• Check wiring and connectors: Visually inspect for frayed wires, corrosion, or loose connectors at the switch and PCM/ECM.
• Test continuity and voltage: Use a multimeter to check for proper voltage supply and ground at the switch terminals, and verify continuity through the switch when pressed.
• Check switch adjustment: Ensure the switch is installed and adjusted according to OEM specs (usually a small clearance at rest).
• Clear the code: After repairs or adjustments, clear the DTC and road test the vehicle to confirm proper operation.
• If the issue persists after all checks, consult OEM diagnostic flowcharts for advanced module testing or reprogramming.

Possible Repairs for Code P0571 #

Most repairs for P0571 are simple and can be performed with basic tools, but always use OEM parts and procedures where possible. The chosen repair will depend on which cause is confirmed during diagnosis:

• Replace faulty brake pedal switch with a new OEM or high-quality aftermarket unit
• Repair or replace damaged wiring between switch and PCM/ECM
• Clean or tighten corroded connectors at the switch and module
• Readjust or properly reinstall the brake switch according to manufacturer specifications
• Replace PCM/ECM only if confirmed defective after exhaustive diagnosis (rare scenario)

Is It Safe to Drive with Code P0571? #

Do not drive the vehicle unless absolutely necessary if the brake lights are not functioning. In most cases, the car will still operate, but a failed brake switch means your brake lights may not illuminate, creating a major safety hazard for you and other drivers. Additionally, systems such as ABS, cruise control, and automatic transmission may not function properly, increasing the risk of unpredictable vehicle behavior. If you must drive, do so only to reach a repair facility, and use extreme caution. Immediate repair is highly recommended for your safety and compliance with traffic laws.

Vehicles Most Commonly Affected by Code P0571 #

While P0571 can appear on virtually any modern vehicle with OBD-II, it is most frequently reported on models from the following manufacturers, often due to switch wear or connector issues:

• Ford (F-150, Focus, Escape, Fusion)
• Chevrolet (Silverado, Malibu, Impala)
• Honda (Accord, Civic, CR-V)
• Toyota (Camry, Corolla, Tacoma)
• Volkswagen (Jetta, Passat, Golf)
• Hyundai (Elantra, Sonata, Tucson)
• Kia (Optima, Forte, Sorento)

Common Mistakes & Best Practices for Code P0571 #

Misdiagnosis of P0571 often stems from skipping basic checks or overlooking the most probable cause. Always start simple and follow a logical diagnostic path to save time and prevent unnecessary part replacement. Keep these best practices in mind:

• Don’t replace the brake switch without verifying power and ground at the connector—wiring faults are common.
• Always check brake light operation before and after repairs; use a helper or a reflective surface if alone.
• Do not ignore brake warning lights or intermittent symptoms—they often precede a full switch failure.
• Use OEM parts for switch replacement whenever possible to ensure proper fit and reliability.
• Record all related DTCs and address them together, as other codes may point to a broader electrical issue.

Express FAQ for Code P0571 #

Is it expensive to fix code P0571?
No, repairs are usually inexpensive. Most fixes involve replacing the brake switch or repairing a connection, which are low-cost parts and quick labor jobs for a professional technician.

Can I fix P0571 myself?
Yes, if you are comfortable with basic tools and electrical checks. Replacing a brake switch or cleaning a connector is within reach for most DIYers. However, always consult your vehicle’s OEM instructions and prioritize safety.