What it means
Brake Booster Motor A Phase U-V-W Circuit Low: the signal voltage is below the expected range. The electric brake booster generates the braking assist; a motor or sensor fault can reduce or disable power-assisted braking. Safety-relevant.
At a glance
- Usually lights the ABS or stability-control warning light
- The engine or gearbox may go into limp mode
How it works
The electric brake booster uses Motor A to provide braking assistance, and its U, V, and W phase circuit carries the motor drive signals. The control module monitors those circuits and sets C0580 when their voltage falls below the expected range, which can limit or disable brake assist.
Common causes
Most likely first.
- Phase shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Brake or ABS warning light
- Brake assist may be reduced or unavailable
How to diagnose it
- Use a scan tool to record freeze-frame data and check brake-booster live data and related codes to see when the low-voltage fault occurred.
- With the vehicle safely parked, inspect Motor A's U, V, and W wiring for chafing or insulation damage that could let a phase wire touch ground.
- Check the Motor A phase connector for corrosion, moisture, loose terminals, or poor pin contact that could add resistance.
- Using the vehicle's wiring information, test each U, V, and W phase circuit for a short to ground and check continuity with power isolated as specified by the manufacturer.
- If the wiring and connections pass, test the booster motor and control module circuits using the manufacturer's diagnostic procedure.
Common fixes
- Repair chafed U, V, or W phase wiring that is shorting to ground.
- Clean or repair corroded or loose Motor A connector terminals.
- Repair or replace damaged sections of the phase harness.
- Replace the brake booster motor or control module only if testing identifies it as faulty.
Can I keep driving?
Because brake assist may be reduced or unavailable, avoid driving if the brake pedal feels unusually hard or braking response changes. Arrange safe transport for diagnosis; continued driving with impaired assist can make stopping harder.
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.