Diagnostic article Generic OBD-II
P0571: brake-switch plausibility is checked against vehicle movement
This GM P0571 monitor counts acceleration or deceleration events that disagree with the reported brake-switch state.
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Documented application
GM 2015 15OBDG09 MW7 transmission-control summary. Only the cited monitor and calibration are described; per-code vehicle and engine applicability has not been established.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
The cited transmission controller evaluates P0571 by comparing the brake-switch state with vehicle acceleration and deceleration events. The purpose is plausibility: a switch signal can exist electrically while reporting a state that does not fit repeated vehicle behavior.
Two types of disagreement are monitored
One branch counts acceleration events while the switch reports on. The other counts deceleration events while it reports off. The table describes a threshold of ten relevant events. This event-based strategy is different from a simple fixed voltage measurement taken with the vehicle parked.
The monitor requires valid operating conditions, including powered components and a supply within the documented range. Output-speed faults also affect its ability to evaluate the relationship. A trustworthy movement signal is therefore part of the evidence, not an unrelated detail.
A communication fault answers another question
The neighboring P0703 description checks the rolling count of the brake-switch network message. Missing messages or an unexpected counter concern communication integrity; P0571 concerns the meaning of the reported switch state relative to movement. Both should be interpreted before assuming that a switch replacement will resolve the complaint.
A technician should preserve the switch status, relevant vehicle-motion data and accompanying faults, then follow the exact transmission and brake-switch procedure. The table does not specify pedal adjustment or identify a failed stop-lamp component. Verification needs credible switch-state transitions and an enabled plausibility test. Deliberately creating unsafe braking or acceleration conditions to accumulate the event count is not an appropriate diagnostic shortcut.
Source and applicability
GM 2015 15OBDG09 MW7 transmission-control summary. Only the cited monitor and calibration are described; per-code vehicle and engine applicability has not been established.
15OBDG09 Transmission Diagnostics, physical PDF page 58.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
Brake Switch A Circuit
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT