P0571, P0572 and P0573 Brake Switch Codes: Symptoms and Safe Checks
A P0571 code, along with P0572 and P0573, points to a problem in the brake switch signal that the control module is monitoring. Drivers often notice cruise control cancellation issues, unusual brake light behavior, or shift interlock trouble. These codes are clues about circuit conditions, not proof a part has failed, so vehicle-specific definitions and careful checks matter before any repair.
Verify What Each Code Means for the Vehicle
Before interpreting a P0571 code, confirm the exact definition and diagnostic steps for the vehicle's year, make, model, and powertrain. Documentation varies, and the monitored brake switch signal and the conditions that set the fault are manufacturer-dependent. In many applications, P0571 identifies a brake switch A circuit malfunction, while a P0572 code describes a circuit low condition and a P0573 code describes a circuit high condition. Those labels refer to the electrical state the module sees, not how far the pedal travels or how hard the driver presses.
Circuit low and circuit high describe voltage or continuity conditions on the stop lamp circuit or related brake pedal position input, not pedal height or braking force. A stored fault is evidence that the module observed an unexpected brake switch signal, not proof the switch itself has failed. Connector damage, wiring faults, supply or ground problems, and incorrect switch adjustment can produce the same codes. Replacement is not justified until the vehicle's procedure identifies the actual fault path.
Symptoms That Can Accompany Brake Switch Circuit Faults
Brake switch circuit faults can leave cruise control unavailable because the module may not trust cruise control cancellation. Brake lights may stay on after the pedal is released, fail to illuminate when the pedal is pressed, or behave normally while another function is affected. Some vehicles also use the same brake light switch path for shift interlock, so moving out of Park can become difficult. Pedal feel can remain ordinary even when the lights or cruise cancel path are not working as intended.
P0573 symptoms are especially easy to misread. A circuit high condition only means the monitored electrical signal sat outside the expected range; it does not predict whether the brake lights will remain on or stay dark. Many switches contain multiple contacts or separate signal paths, so the stop lamps can still light while a cruise or interlock circuit reports a fault. Symptoms also vary by vehicle design. Normal pedal travel and firm braking do not confirm that brake lights, cruise cancellation, or the shift interlock are operating correctly.
Safe Brake Light and Pedal Observations
Park the vehicle, secure it, and place the ignition or power mode in the operating state the owner's manual specifies for brake lamp checks. With a helper watching from behind, or by using a reflection, observe all brake lights, including the center high-mounted lamp when the vehicle has one. Apply gentle pedal pressure and note whether the lights come on, then release the pedal and confirm they go out. Do not reach into moving pedal hardware while making these observations.
Look for a floor mat that could hold the pedal down, and watch whether the pedal returns on its own after release. Missing brake lights or lights that stay on after the pedal is up need prompt attention because following traffic may not receive a clear stop signal. If braking feels abnormal or the pedal does not return, stop using the vehicle and arrange professional help. Do not road-test cruise control, bypass the brake light switch, or override the shift interlock to investigate these codes.
Possible Causes and the Limits of Visual Checks
Possible causes include a malfunctioning brake light switch, incorrect installation or adjustment, damaged mounting hardware, and problems at a pedal contact or stopper when the vehicle uses those parts. Loose connectors, damaged wiring, missing supply or ground, and shorts or open circuits can also set P0571, P0572, or P0573 depending on how the circuit is designed. Owner inspection should stay limited to accessible visual observations of the pedal area, the switch body, and obvious connector damage. Do not bridge terminals, probe energized circuits, or work near restraint wiring.
Seeing the lights stay on or go dark, or reading circuit low versus circuit high on a scan, still cannot identify a failed component by itself. The same wording can result from an open, a short, a poor ground, or a switch that is out of position, and only the wiring diagram plus electrical testing can sort those paths. Visual checks help when a connector is unseated or a mount is broken, but they cannot confirm signal integrity. Treat the code as a starting point, not a parts list.
What a Related P0504 Code Adds to Diagnosis
A related P0504 code generally indicates a brake switch A/B correlation concern, meaning the control module compared two related brake signals and found they did not agree. Verify that definition for the specific vehicle before treating it as a diagnosis. Working brake lights do not prove every monitored path is correct, because one contact can still operate the lamps while another signal used for cruise or correlation is wrong. P0504 adds context to the P0571 family; it is not proof the switch has failed.
A technician typically reviews accompanying codes, freeze-frame data, and scan tool live data for brake switch status while the pedal is applied and released. Live data can show whether one signal changes with pedal movement while another stays stuck, which helps separate a correlation problem from a single-circuit low or high condition. Those readings still need the vehicle's wiring information to interpret. A P0504 result belongs in that circuit investigation; it should not, by itself, be treated as a reason to replace the switch.
Adjustment, Repair and Confirmation of Correct Operation
Adjustment depends on switch design. Some brake light switches self-adjust as they are installed against the pedal, while others require a specified setup or replacement rather than improvised positioning. Follow the applicable service procedure before any adjustment, and do not rotate, pull, or reposition the switch using a generic method. Professional testing of switch signals, circuit supply, grounds, and wiring should come before selecting a repair so the work matches the confirmed fault instead of the most convenient part.
Repair may involve the switch, mounting or pedal contact components, connectors, or wiring, according to what testing actually finds. After the work, confirm that the brake lights illuminate with gentle pedal pressure and turn off on release, that the pedal returns fully, and that monitored brake switch signals on scan tool live data change as expected. Clearing a stored P0571, P0572, or P0573 code by itself does not verify success. Correct operation of the lights, pedal return, and related functions such as cruise enable and shift interlock is the real confirmation.