P0571 Code: Here's How to Solve It Fast

The P0571 diagnostic trouble code (DTC) is related to a malfunction in the cruise control brake switch circuit. This code is typically triggered when the vehicle's powertrain control module (PCM) detects an issue with the operation of the brake light switch or the cruise control/brake switch "A" circuit. Understanding and resolving this code is crucial for maintaining proper functionality of your vehicle's cruise control system and ensuring safe operation on the road.

P0571 Code Meaning	P0571 Code Common Causes
Cruise Control/Brake Switch A Circuit Malfunction	Defective cruise control/brake switch
PCM detects an issue with brake switch operation	Wiring problems in the brake switch circuit
Malfunction in the cruise control system	Faulty Powertrain Control Module (PCM)
Brake switch signal inconsistency	Corroded or loose electrical connections
Safety feature to prevent unintended acceleration	Blown fuse in the brake switch circuit

Understanding the P0571 Code

The P0571 code is a generic powertrain code that applies to various makes and models of vehicles equipped with OBD-II systems. This code specifically relates to the cruise control and brake switch circuit, which plays a crucial role in the safe operation of your vehicle's cruise control system.

Symptoms of P0571 Code

When your vehicle triggers the P0571 code, you may experience one or more of the following symptoms:

• Illuminated check engine light
• Cruise control system fails to engage or operate properly
• Erratic cruise control behavior
• Brake lights may not turn on when the brake pedal is pressed
• Difficulty shifting out of park (in some vehicles with an interlock system)

These symptoms can vary depending on the severity of the issue and the specific make and model of your vehicle. It's important to address the problem promptly to ensure the safe operation of your vehicle's cruise control and braking systems.

Technical Explanation

The cruise control brake switch, also known as the brake pedal position sensor in some vehicles, is responsible for sending a signal to the PCM when the brake pedal is pressed. This signal is crucial for disengaging the cruise control system and illuminating the brake lights. When the PCM detects an inconsistency or malfunction in this circuit, it triggers the P0571 code.

The "A" in the code description typically refers to a specific circuit, connector, or harness within the brake switch system. The exact definition may vary slightly between vehicle manufacturers, so it's essential to consult your vehicle's specific repair manual for precise information.

Diagnosing the P0571 Code

Proper diagnosis of the P0571 code requires a systematic approach and some basic automotive knowledge. Here's a step-by-step guide to help you diagnose the issue:

1. Connect an OBD-II scanner to your vehicle's diagnostic port and retrieve all stored codes and freeze frame data.
2. Clear the codes and test drive the vehicle to see if the P0571 code returns.
3. If the code returns, visually inspect the brake light switch and its wiring for any obvious signs of damage, corrosion, or loose connections.
4. Check the brake light fuse and replace it if blown.
5. Use a multimeter to test the continuity and resistance of the brake light switch when the pedal is pressed and released.
6. Inspect the wiring harness connected to the brake switch for any signs of damage, fraying, or exposed wires.
7. Test the voltage at the brake switch connector with the ignition on to ensure proper power supply.
8. If all physical components appear to be in good condition, use a scan tool to monitor the brake switch input while operating the brake pedal.

Warning: If you're not comfortable performing these diagnostic steps or lack the necessary tools, it's best to consult a professional mechanic to avoid potential safety risks or further damage to your vehicle.

Common Causes and Solutions for P0571 Code

1. Faulty Brake Light Switch

The most common cause of the P0571 code is a defective brake light switch. This switch can wear out over time or become misaligned, causing intermittent or complete failure.

Symptoms:

• Brake lights don't illuminate
• Cruise control doesn't disengage when brakes are applied
• Difficulty shifting out of park (in vehicles with an interlock system)

Diagnosis:

1. Locate the brake light switch near the top of the brake pedal.
2. Inspect the switch for any visible damage or misalignment.
3. Use a multimeter to test the switch's continuity when the brake pedal is pressed and released.

Solution:

If the brake light switch is found to be faulty, replace it with a new one. This is typically an inexpensive and straightforward repair that can often be done at home.

Cost Estimate:

• Parts: $20 - $50
• Labor: $50 - $100 (if professional installation is required)

2. Wiring Issues in the Brake Switch Circuit

Damaged or corroded wiring in the brake switch circuit can cause intermittent signals or complete failure, triggering the P0571 code.

Symptoms:

• Intermittent cruise control operation
• Flickering brake lights
• Multiple electrical issues

Diagnosis:

1. Visually inspect the wiring harness connected to the brake switch.
2. Look for signs of damage, fraying, or exposed wires.
3. Check for corrosion or loose connections at the brake switch connector.
4. Use a multimeter to test for continuity along the wiring harness.

Solution:

Repair or replace any damaged wiring. Clean corroded connections and ensure all connectors are securely fastened.

Cost Estimate:

• DIY Repair: $10 - $50 for materials
• Professional Repair: $100 - $300, depending on the extent of the damage

Warning: Working with vehicle electrical systems can be dangerous. If you're not confident in your ability to safely repair wiring, consult a professional mechanic.

3. Blown Fuse

A blown fuse in the brake switch circuit can cause the P0571 code to appear.

Symptoms:

• Complete loss of brake lights
• Non-functional cruise control

Diagnosis:

1. Locate the fuse box (refer to your vehicle's manual for the exact location).
2. Find the fuse associated with the brake lights/cruise control system.
3. Visually inspect the fuse or use a multimeter to test for continuity.

Solution:

If the fuse is blown, replace it with a new one of the same amperage rating. If the fuse blows again immediately, there may be a short circuit in the system that requires further investigation.

Cost Estimate:

• Parts: $1 - $5 for a new fuse
• Labor: DIY or minimal if done during a regular service

4. Faulty Powertrain Control Module (PCM)

In rare cases, the P0571 code may be caused by a malfunction within the PCM itself.

Symptoms:

• Multiple error codes present
• Various electrical and engine performance issues

Diagnosis:

This typically requires advanced diagnostic equipment and should be performed by a professional mechanic.

Solution:

If the PCM is determined to be faulty, it will need to be replaced or reprogrammed by a qualified technician.

Cost Estimate:

• PCM Replacement: $500 - $1000+
• PCM Reprogramming: $150 - $300

Note: PCM issues are relatively rare and should only be considered after ruling out all other potential causes.

Preventing Future P0571 Codes

To minimize the risk of encountering the P0571 code in the future, consider the following preventive measures:

• Regularly inspect the brake light switch and surrounding wiring for signs of wear or damage.
• Keep the area around the brake pedal clean and free from debris that could interfere with the switch operation.
• Address any electrical issues promptly to prevent cascading failures.
• Follow your vehicle's recommended maintenance schedule to ensure all systems are functioning properly.

Conclusion

The P0571 code, while not immediately critical, can indicate issues that may compromise the safety features of your vehicle, particularly the cruise control system. By understanding the causes and following the diagnostic steps outlined in this guide, you can often identify and resolve the issue quickly and cost-effectively. However, if you're unsure about any aspect of the diagnosis or repair process, it's always best to consult with a qualified mechanic to ensure the safety and reliability of your vehicle.

Frequently Asked Questions About P0571

• Can I drive my car with the P0571 code?
  While it may be possible to drive, it's not recommended as your cruise control and potentially your brake lights may not function correctly. This can pose a safety risk, especially on highways or in heavy traffic.
• How urgent is it to fix the P0571 code?
  It's important to address this code promptly. While not an immediate engine threat, it affects safety systems like cruise control and potentially brake lights, which are crucial for safe driving.
• Will the P0571 code clear itself?
  It's unlikely that the code will clear itself unless it was triggered by a temporary glitch. In most cases, the underlying issue needs to be resolved before the code will clear permanently.
• How much does it typically cost to fix a P0571 code?
  Costs can vary widely depending on the cause. Simple fixes like replacing a brake light switch might cost $50-$150, while more complex issues involving wiring or the PCM could range from $200 to over $1000.
• Can a P0571 code be caused by a dead battery?
  A dead battery itself won't cause a P0571 code. However, a weak battery or recent battery replacement might cause temporary electrical glitches that could trigger the code.
• Is it safe to clear the P0571 code without fixing the problem?
  It's not recommended to clear the code without addressing the underlying issue. The code will likely return, and you risk driving with malfunctioning safety systems.
• Can weather conditions affect the P0571 code?
  Extreme weather conditions, particularly moisture and corrosion from road salt, can affect electrical connections and potentially trigger a P0571 code. Regular maintenance can help prevent weather-related issues.
• How long does it take to diagnose and fix a P0571 code?
  Diagnosis typically takes 1-2 hours. Repair time varies based on the cause – from 30 minutes for a simple switch replacement to several hours for complex wiring issues.