What it means
Open circuit on one of the three U/V/W phases of brake booster motor A (3-phase BLDC motor in electric brake boosters).
At a glance
- Usually lights the ABS or stability-control warning light
- The engine or gearbox may go into limp mode
How it works
Brake booster motor A is a three-phase brushless motor driven through U, V, and W phase circuits. C057F sets when the module detects an open in one or more of those phase paths, which can prevent motor A from providing brake assist.
Common causes
Most likely first.
- Phase wire open or motor winding open
- Pin pushed back out of connector body
- Cracked solder joint inside the module or sensor
Symptoms
- Brake or ABS warning light
- Brake assist may be reduced or unavailable
How to diagnose it
- Scan the brake system for freeze-frame data and related motor or assist codes, and check whether motor A is reported as unavailable.
- With the vehicle secured and the system powered down as specified by the manufacturer, inspect motor A's connector and phase wiring for damage, corrosion, or a terminal pushed back.
- Check that the connector is fully seated and its terminals make firm contact, since a loose pin can interrupt a motor phase.
- Using the wiring diagram and manufacturer's safety procedure, test continuity of each U, V, and W phase path and inspect for an open winding.
- If all phase paths and motor windings pass, follow the manufacturer's procedure to test the motor driver and control module.
Common fixes
- Reconnect and secure motor A's connector.
- Repair a damaged or open U, V, or W phase wire.
- Repair or replace a loose or corroded phase terminal.
- Replace brake booster motor A if an open winding is confirmed.
- Repair or replace the motor driver or control module only if the phase wiring and motor pass testing.
Can I keep driving?
Treat this as an urgent brake-assist fault: avoid driving if assist is reduced or unavailable, since stopping may require much greater pedal force. Arrange safe transport for inspection, and do not continue if the pedal feels unusually hard or braking is impaired.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.