What it means
Brake Booster Motor A Position Sensor Circuit Low: the signal voltage is below 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. C0588 sets when the sensor signal voltage falls below its expected range, which can prevent reliable position feedback and lead the module to limit or disable brake assist.
Common causes
Most likely first.
- Signal wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
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 low signal began.
- Inspect the sensor signal wire for chafing or damaged insulation that could let it short to ground.
- Check the Motor A position-sensor connector for corrosion, moisture, loose terminals, or poor contact.
- Using the wiring information, test the signal circuit for a short to ground and check continuity with power isolated as specified by the manufacturer.
- If the harness and connector pass, test the position sensor and module input according to the manufacturer's procedure.
Common fixes
- Repair a signal wire shorted to ground.
- Clean or repair corroded or loose position-sensor connector terminals.
- Repair or replace damaged sections of the sensor harness.
- Replace the position sensor or control module only if testing confirms it is faulty.
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.