Chassis, generic

C0581 Brake Booster Motor A Phase U-V-W Circuit High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Upper bridge transistor in the brake module shorted or stuck on
Phase lead of motor A shorted to battery voltage
Moisture in the booster connector creating a leakage path to supply

Symptoms

  • Brake assist switched off, high pedal effort
  • Brake system warning lamp and service message

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–2,800
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

brake booster motor amotor phase wiring

Related codes

C057FC0580C0582C0585

References: ti.com, ti.com, gsi.ext.gm.com.