What it means
Brake Booster Motor B Position Sensor Circuit/Open: the circuit is open. 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 helps provide power-assisted braking, and its position sensor reports the motor's movement. The brake control module monitors the sensor circuit for a usable signal; it sets C058B when the motor B position signal path is open and the reading is lost.
Common causes
Most likely first.
- Signal wire 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
- Record freeze-frame data and check for related brake or booster codes to identify whether the motor B signal disappeared with other circuit faults.
- Inspect the motor B position sensor connector for a backed-out pin, loose fit, corrosion, or damage.
- Trace the motor B sensor signal wire and harness for a break, pull, or chafe point that could interrupt continuity.
- With the circuit isolated as specified by the manufacturer, check continuity through the motor B signal path and inspect terminal fit at both ends.
- If the external wiring and terminals pass, test the sensor and module connections for an internal open in line with manufacturer procedures.
Common fixes
- Reseat and secure a pushed-back motor B connector terminal.
- Repair an open or damaged motor B position sensor signal wire.
- Restore a poor connector contact or solder connection where serviceable.
- Replace the failed motor B position sensor or module only after confirming the open is internal.
Can I keep driving?
The brake booster may provide reduced or no power assist, so the pedal can require much more force and stopping distance can increase. Avoid driving and arrange transport if the brake warning is on or assist feels reduced.
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.