What it means
Brake Booster Motor B 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 electric brake booster uses motor B and its position sensor to help control braking assist. The brake control module monitors the sensor supply and sets C05BE when the circuit voltage is higher than expected, such as when the supply wire contacts battery voltage.
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
- Scan the brake control module for related codes and freeze-frame data to identify when motor B's position-sensor supply went high.
- Inspect the sensor supply wire along its route for pinching or contact with a battery-positive source.
- Check the motor B sensor connector for corrosion, loose terminals, or bridging between terminals.
- Using the wiring diagram, test for a short from the supply circuit to battery voltage, following the manufacturer's procedure.
- Repair the fault, clear the code, and confirm the supply returns to the manufacturer's specification.
Common fixes
- Reposition and secure a pinched supply wire away from battery-positive wiring.
- Repair insulation damaged where the supply wire contacted a B+ source.
- Clean or replace corroded or damaged connector terminals.
- Replace the sensor or repair the module only if testing confirms an internal fault.
Can I keep driving?
The fault can disable stability control and may reduce brake assist; avoid driving until the braking system is confirmed to work normally. If pedal effort or braking response is abnormal, stop safely and 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.