P0571
Brake Switch "A" Circuit Malfunction
The brake light switch signal seen by the ECU is implausible — for example, both contacts active simultaneously, or no signal change despite the brake pedal being pressed (cruise control engages and disengages on this signal). On many cars also disables shift interlock.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: easy
Common causes
Ordered by how often each turns out to be the cause.
- Brake switch failed (worn contacts, internal break)Common
- Switch misadjusted (does not actuate at correct pedal position)Possible
Parts involved
- Brake Light Switch
- Brake Light Switch Wiring
P0571 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.