Chassis, generic

C057F Brake Booster Motor A Phase U-V-W Circuit/Open

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C057F covers an interrupted drive path in the three-phase motor of an electric brake booster: a winding, a phase lead or a power transistor that no longer carries current. GM documents it in several brake modules, always as Type A with MIL after one trip. Its 2016 and 2019 hybrid tables switch single bridge transistors while the motor is not being driven and set the code within 5 ms if the phase W voltage does not respond. The 2023 and 2025 EBCM tables measure coil resistance and trip above 0.20358 Ω (or below 0.01258 Ω) for 0.12 s, or when the voltage vector is off by more than 1.5 V. In GM's 2019 IBC unit C057F also covers phases that fail to rise above 3.46 V or sit near battery level before start-up. The brakes keep working, only without electric assist.

Likely causes

Bridge transistor in the brake module no longer switching (drive stage defect)
Broken winding or failed internal phase connection in booster motor A
Corroded or loose phase contact between control unit and motor, raising coil resistance

Symptoms

  • Hard brake pedal, noticeably more pedal force needed
  • Brake system, ABS/traction and check engine lamps on
  • Message about reduced brake assist

Repair estimate

DifficultyHardWorkshop job
Parts and labour€200–2,800
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

C0580C0581C0582C0583C0590

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