P0571 means Brake Switch A Circuit. The computer has found a fault in the brake switch A circuit, so it cannot reliably tell when the brakes are applied. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0571 means
Most engine sensors receive a 5-volt reference and return a signal between roughly 0 and 5 volts. Codes ending in circuit high or circuit low usually point to an electrical fault: an open circuit, a short or an unplugged connector. Range/performance codes mean a signal is present but disagrees with what the computer expects from the other sensors, which more often points to a dirty sensor, an air leak or a mechanical problem.
P0571 symptoms
- Cruise control not working
- Brake lights not working or stuck on
- Shifter stuck in park on some vehicles
- Check engine light
Common causes of P0571
- Failed or misadjusted brake light switch
- Blown brake light fuse
- Wiring or connector fault
- Broken pedal stop bumper
How to diagnose P0571
- Check brake light operation
- Check the brake light fuse
- Watch the brake switch input on a scan tool
Can you drive with P0571?
Make sure the brake lights work before driving.
P0571 tips
Check that the brake lights work, and ask a helper to watch while you press the pedal; a failed switch can leave them stuck on or off.
Will P0571 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0571 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0504 | Brake Switch A/B Correlation |
| P0703 | Brake Switch B Input Circuit |
| P0500 | Vehicle Speed Sensor A Malfunction |
Guides that help
When it is more than a sensor
Sensor codes are usually fixed with a sensor, a connector, wiring or a leak repair rather than major parts. If testing turns up internal engine trouble instead, see how to tell if an engine is blown and compare engines by code on our engines page.
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