C0571
Active Brake Assist Performance
The brake assist or driver assistance module has detected that brake assist performance is degraded. The system may fail to autonomously build pressure during emergency braking and emergency brake assist functions are limited.
- Check engine light: Not always
- Emissions related: No
- Repair difficulty: hard
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Common causes
Ordered by how often each turns out to be the cause.
- Active booster slow or weakCommon
- Secondary fault on related sensorPossible
- System calibration required after repairLess likely
Parts involved
- Active Brake Booster
- Brake Assist Module
- Brake Pressure Sensor
C0571 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.