What it means
Brake Booster Motor A 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
The Motor A position sensor reports the brake-booster motor's position so the control module can manage assisted braking. C0587 sets when the sensor circuit is open, interrupting the signal and potentially causing the module to limit or disable brake assist.
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
- Use a scan tool to record freeze-frame data and check Motor A position live data and related codes for signs of a lost or missing signal.
- Inspect the position-sensor connector and harness for a disconnected plug, broken wire, pushed-back pin, or visible damage.
- Check the connector terminals for corrosion or poor contact and confirm they seat securely.
- Using the vehicle's wiring information, test signal-wire continuity and the sensor circuit connections with power isolated as specified by the manufacturer.
- If the external wiring passes, test the position sensor and module connection using the manufacturer's diagnostic procedure.
Common fixes
- Reconnect a loose Motor A position-sensor plug after checking the terminals.
- Repair a broken or open signal wire in the Motor A sensor circuit.
- Restore a pushed-back or corroded connector terminal.
- Replace the position sensor or control module only if testing confirms the fault is internal.
Can I keep driving?
Brake assist may be reduced or unavailable, so do not continue driving if the pedal feels harder or braking response changes. Arrange safe transport for diagnosis because stopping may require more effort.
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.