P0571 Cruise Control/Brake Switch A Circuit Malfunction

P0571 points to a cruise control or brake switch A circuit malfunction. The brake-switch signal does not match expected pedal or cruise-control logic.

Code details

Generic OBD-II · P0

System: Speed / Idle
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not diagnose cruise control before confirming brake-switch data; a bad brake input can disable cruise and affect shift strategy.

Symptoms of P0571

Unstable, high, or low idle, or stalling.
Erratic speedometer, cruise-control, or shift behaviour.
Check-engine light with a hesitation or surge.

Common causes of P0571

A dirty throttle body, idle-control valve, or throttle-position sensor.
A failing vehicle-speed or wheel-speed sensor, or its wiring.
Vacuum leaks or a related sensor forcing the idle/speed strategy.

Useful checks before replacing parts

Compare brake switch input data with actual pedal movement, brake lamp operation, cruise cancel behavior, and shift-interlock operation.
Inspect brake switch adjustment, connector condition, wiring, fuse feeds, and water intrusion near the pedal area.
Check for multiple brake-switch circuits on the vehicle because redundant inputs may disagree.

Related OBD-II codes

These nearby speed / idle entries can help compare wording and pin down the fault area.