The P0571 code is a generic OBD-II diagnostic trouble code indicating “Cruise/Brake Switch ‘A’ Circuit Malfunction.” It means the powertrain control module detected an electrical fault or erratic signal in the primary brake switch circuit.
This code does not automatically prove the brake switch has failed. Diagnosis requires verifying brake light operation, checking switch adjustment, and testing the circuit wiring before replacing any components.
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Key Takeaways
- The P0571 code indicates the control module detected a circuit malfunction involving the primary brake pedal position switch.
- Possible causes include a misadjusted switch, failed internal contacts, damaged wiring, or a blown fuse.
- Diagnosis involves verifying brake light operation, inspecting switch alignment, and testing circuit continuity and voltage.
- Repairs may involve adjusting the switch, repairing wiring, or replacing the confirmed failed brake switch assembly.
P0571 Code Description and Implications
The P0571 code indicates that the powertrain control module detected a malfunction in the brake switch “A” circuit. This generic OBD2 error code applies to many vehicles equipped with cruise control and electronic transmission controls.
The module uses the brake switch signal to disengage cruise control, unlock the torque converter clutch, and manage shift interlocks. It monitors the circuit for electrical continuity and logical signal correlation.
When the module detects an open circuit, a short, or an illogical signal state while driving, it stores this code. This is an electrical or logical circuit fault, not necessarily a hydraulic brake system failure.
Common Causes of the P0571 Code
A misadjusted or mechanically binding brake pedal position switch is a primary cause. If the switch plunger does not fully extend or retract with the pedal, it sends an erratic signal.
Internal electrical failure within the brake switch can cause open or shorted contacts, preventing the module from receiving a valid brake pedal status signal.
Damaged wiring, chafed insulation, or corroded connectors in the brake switch harness will interrupt the reference voltage, signal, or ground paths.
A blown fuse supplying power to the brake switch circuit or the stop lamp circuit will also result in a complete loss of signal to the control module.
Symptoms Associated With P0571
An illuminated Check Engine Light is expected once the monitor detects the circuit malfunction. MIL behavior varies by application, but the light commands when the fault is verified.
Cruise control will likely become inoperative or fail to engage, as the module requires a valid brake switch signal to safely activate the system.
You may experience torque converter clutch lockup issues, causing poor fuel economy or engine stalling when coming to a stop. The shift interlock may also prevent shifting out of park.
Diagnosing the P0571 Trouble Code
Diagnosis must begin by confirming the exact factory definition and checking for related stop lamp or cruise control codes. Record freeze-frame data to see the vehicle speed and brake status when the code set.
Verify the operation of the rear brake lights. If the brake lights do not illuminate when the pedal is pressed, the issue is likely a blown fuse, bad switch, or open circuit.
Inspect the brake switch mounting and adjustment. Ensure the switch plunger is properly seated against the brake pedal lever and moves through its full range of travel.
Use a multimeter to test the switch for proper continuity and resistance changes as the pedal is depressed. Check the wiring harness for reference voltage, ground, and signal continuity.
Repairing the P0571 Issue
Repairs must follow confirmed diagnosis. If the brake switch is misadjusted, loosen the mounting hardware and adjust the switch position to match the manufacturer specification.
If the wiring harness is damaged or connectors are corroded, repair the circuit and secure the harness to prevent future rubbing or moisture intrusion.
If electrical testing confirms the brake switch is internally faulty, replace the switch using a component meeting the exact vehicle specification. Clear the codes and verify brake light operation.
Cost Considerations for P0571 Repairs
Cost depends on diagnostic time, component accessibility, required parts, programming requirements, and labor.
Replacing a standard mechanical brake switch involves minimal parts and labor expenses, as it is usually located directly under the dashboard near the pedal assembly.
If the vehicle uses an integrated electronic pedal position sensor assembly or requires extensive wiring harness repair, the overall repair cost will increase.
Prevention Strategies for Future Occurrences
Inspecting the brake switch mounting bracket and pedal pad for wear or damage during routine service can help prevent the switch from becoming misadjusted or physically damaged.
Keeping the under-dash area clear of debris and ensuring floor mats do not interfere with the brake pedal travel helps maintain proper switch operation.
Some internal electrical switch failures occur due to normal component aging and cannot be reliably prevented through standard maintenance.
Troubleshooting Tips and Best Practices
Do not assume the brake switch is faulty simply because a circuit malfunction code is stored. A simple blown stop lamp fuse or bad ground connection is a very common cause.
Always verify the brake light operation before replacing the switch. If the brake lights work perfectly, the issue may lie in a secondary signal wire dedicated only to the control module.
Check for technical service bulletins for your exact vehicle application. Some manufacturers release updated brake switch designs or revised pedal brackets to address chronic misalignment issues.
More OBD-II Codes
| P0563 | P0562 | P0560 | P0556 |
| P0551 | P0550 | P0572 | P0573 |
| P0579 | P057C | P0581 | P0597 |
| P0500 | P0501 | P0504 | P0505 |
| P0700 | P0705 | P0715 | P0720 |
| P0722 | P0730 | P0740 | P0741 |
Frequently Asked Questions
Is the P0571 code generic or manufacturer-specific?
Yes, P0571 is a generic SAE OBD-II diagnostic trouble code. However, the exact brake switch design and diagnostic steps vary by manufacturer and vehicle application.
Can a bad brake light fuse cause a P0571 code?
Yes. The brake switch often shares a power supply circuit with the rear stop lamps. A blown stop lamp fuse will cut power to the switch, causing a circuit malfunction code.
Will a P0571 code disable my cruise control?
It typically will. The control module requires a valid brake switch signal to safely engage the cruise control system. If the circuit is faulty, cruise control is disabled.
Does a P0571 code mean my brakes are failing?
Not necessarily. This code indicates an electrical or logical fault in the brake switch signal circuit, not a hydraulic failure of the physical brake calipers, pads, or master cylinder.
Can I clear the P0571 code without fixing the problem?
Clearing the code only resets the warning light. If the underlying wiring fault, blown fuse, or misadjusted switch remains, the monitor will detect the malfunction immediately and turn the light back on.
What Should You Do About the P0571 Code?
Confirm the exact factory definition and check for related stop lamp codes for your specific vehicle application. Follow the applicable manufacturer diagnostic procedure to verify whether the fault lies in the switch adjustment, wiring, or the brake switch itself.
Once testing confirms the root cause, repair or replace the confirmed failed component, then retest the brake lights and cruise control operation to ensure proper system function.
