What it means
Brake Booster Motor A Position Sensor Supply 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
The position sensor for brake booster motor A reports the motor's position to the brake control module through its supply circuit. This code sets when the circuit signal is implausible or outside the valid range, rather than simply being detected as low or high. High connector resistance, a drifting sensor, or loose sensor mounting can make the reading unreliable and affect electric brake assistance.
Common causes
Most likely first.
- Connector with high resistance
- Sensor element aged beyond calibration window
- Sensor mounting loose - signal damping
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
How to diagnose it
- Review brake-module freeze-frame and live data to confirm the motor A sensor supply reading is out of range and check for related booster faults.
- Inspect the sensor and its mounting for looseness or damage that could affect the position reading.
- Check the supply-circuit connector for corrosion, poor terminal contact, or other signs of high resistance.
- Test the circuit and compare its readings with the manufacturer's specification while checking for changes as the motor position changes.
- If the wiring and mounting pass, test the position sensor and brake control module supply output according to the manufacturer's procedure.
Common fixes
- Secure the motor A position sensor if its mounting is loose.
- Clean or replace high-resistance connector terminals.
- Repair damaged supply wiring or poor connections.
- Replace the position sensor if it remains outside the valid range with the circuit verified.
- Repair the module supply output only if testing identifies it as faulty.
Can I keep driving?
The unreliable motor position signal can reduce or disable power-assisted braking, and the vehicle may enter a limited operating mode. Stop safely and arrange recovery if brake effort or performance is 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.