What it means
Brake Booster Motor B Position Sensor Circuit High: the signal voltage is above 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
Brake booster motor B supplies power-assist force, and its position sensor sends motor movement information to the brake control module. The module sets C058D when the sensor signal rises above its expected range, such as when the signal is shorted to a power source or the circuit connection is faulty.
Common causes
Most likely first.
- Signal wire shorted to battery
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Brake or ABS warning light
- Brake assist may be reduced or unavailable
How to diagnose it
- Review freeze-frame data and live motor B position readings to establish whether the signal was high continuously or only during booster operation.
- Inspect the motor B position sensor harness for pinching or damaged insulation where it could contact a battery-positive or other powered wire.
- Check the sensor connector for corrosion, loose terminals, or signs of heat or water damage that could disrupt the signal.
- Test the motor B signal circuit for a short to power and verify wiring continuity using the manufacturer's procedure.
- If the harness and connector are sound, test sensor output and module input against the manufacturer's specifications to locate an internal fault.
Common fixes
- Repair pinched motor B sensor wiring that contacts a power source.
- Restore damaged, corroded, or loose connector terminals.
- Replace a motor B position sensor that produces an out-of-range high signal despite a sound circuit.
- Repair or replace the brake control module only after excluding wiring and sensor faults.
Can I keep driving?
The booster may lose or limit power assist, which can make braking harder and increase stopping distance. Do not continue driving if pedal effort or braking response is abnormal; have the vehicle transported for diagnosis.
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.