C0581Brake Booster Motor A Phase U-V-W Circuit High
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- C0581 is reserved for a phase of booster motor A whose voltage sits too high – typically a phase lead touching battery positive or an upper power transistor that stays conductive. No manufacturer publishes C0581: GM's brake tables list only C057F, C0580 and C0582 for the phase circuits of this motor, and its 2019 IBC unit books stuck-high phases under C057F. How such a fault is detected is laid out in gate-driver data sheets: TI's DRV8343-Q1 runs an offline short-to-supply test while the bridge is off, and the DRV3245Q-Q1, intended for electric brake and brake assist, watches drain-source voltages and phase comparators. Because a stuck upper transistor can lock the motor, the module turns assist off; the hydraulic base brake stays available.
- What you may notice
- Brake assist switched off, high pedal effort
- Brake system warning lamp and service message
- Likely causes
- LikelyUpper bridge transistor in the brake module shorted or stuck on
- PossiblePhase lead of motor A shorted to battery voltage
- RareMoisture in the booster connector creating a leakage path to supply
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €2,800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.