What it means
Brake Booster Motor A 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
The Motor A position sensor reports the brake-booster motor's position to the control module. C0589 sets when that sensor signal rises above its expected range, which can result from a signal wire contacting battery power and may cause the module to limit or disable brake assist.
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
- Use a scan tool to record freeze-frame data and check Motor A position live data and related codes for when the high signal began.
- Inspect the sensor signal wire for pinching or chafing where it could touch battery power or another powered circuit.
- Check the position-sensor connector for corrosion, loose terminals, or damaged insulation.
- Using the vehicle's wiring information, test the signal circuit for a short to power and verify continuity as specified by the manufacturer.
- If the wiring and connector pass, test the position sensor and module input using the manufacturer's procedure.
Common fixes
- Repair the signal wire where it is shorted to a power source.
- Clean or repair damaged, corroded, or loose position-sensor connector terminals.
- Repair or replace a pinched or chafed section of the sensor harness.
- Replace the position sensor or control module only if testing confirms a fault.
Can I keep driving?
Brake assist may be reduced or unavailable, so avoid driving if pedal effort or braking response has changed. Arrange safe transport for diagnosis if braking feels abnormal; continued driving 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.