What it means
Brake Booster Motor A Position Sensor Circuit Range/Performance: the signal is implausible or outside the valid 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 A helps provide power-assisted braking, and its position sensor reports how the motor is moving. The brake control module checks whether that signal changes plausibly as the booster operates; it sets C058A when the motor A position reading is outside the expected range or does not match the expected movement.
Common causes
Most likely first.
- Sensor reading drifted
- Sensor element aged beyond calibration window
- Sensor mounting loose - signal damping
Symptoms
- Brake or ABS warning light
- Brake assist may be reduced or unavailable
How to diagnose it
- Record freeze-frame data and compare motor A commanded position with its reported position during booster operation to see when the readings diverge.
- Inspect the motor A position sensor mounting and connector for looseness, damage, or contamination that could make the reading unstable.
- Check the sensor wiring and connector terminals for poor contact, corrosion, or damage that could distort the signal.
- Use a scan tool to observe the motor A position signal through its operating range and look for drift, jumps, or readings that do not follow commanded movement.
- Test the motor A position sensor and its circuit against the manufacturer's specifications, then assess the sensor or brake control module only if the wiring checks pass.
Common fixes
- Secure a loose motor A position sensor or connector.
- Repair damaged or poorly connected motor A sensor wiring or terminals.
- Replace a motor A position sensor that drifts or fails its range checks.
- Replace or repair the brake control module only after the sensor and circuit are verified.
Can I keep driving?
Treat this as a brake-system fault: power assist may be reduced or lost, increasing pedal effort and stopping distance. Avoid driving; if braking feels abnormal, have the vehicle transported for repair.
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.