What it means
Brake Booster Motor A Position Sensor Supply 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 position sensor for brake booster motor A uses a supply circuit to send motor position information to the brake control module. This code sets when the supply circuit voltage is higher than expected. A short to battery voltage, corroded connector pins, or a pinched wire touching a power feed can cause the high reading and disrupt booster operation.
Common causes
Most likely first.
- Supply wire shorted to battery
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
How to diagnose it
- Check brake-module freeze-frame and live data to verify that the motor A position sensor supply is high and look for related booster faults.
- Inspect the sensor connector and supply harness for pinching, corrosion, or contact with a battery-voltage source.
- Use the wiring diagram to check for a short between the motor A sensor supply circuit and battery voltage.
- Inspect terminal fit and verify circuit continuity between the sensor and brake control module.
- If the harness checks out, test the sensor and module supply output according to the manufacturer's specification.
Common fixes
- Repair a pinched wire contacting a power feed.
- Clean or replace corroded sensor connector terminals.
- Repair a short to battery voltage in the supply circuit.
- Replace the position sensor if it causes the high reading and the wiring is sound.
- Repair the module supply output only if testing confirms it is faulty.
Can I keep driving?
This fault can reduce or disable power-assisted braking and may put the vehicle into a limited operating mode. Do not drive if the pedal is unusually hard or braking feels reduced; arrange recovery.
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.