What it means
Brake Booster Motor B Current Sensor 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 electric brake booster uses a motor to provide braking assistance, and a current sensor monitors motor B's electrical draw. This code sets when the sensor signal is implausible or outside the expected range, so the control module may not be able to assess motor B operation correctly.
Common causes
Most likely first.
- Sensor reading drifted
- 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
- Save freeze-frame data and check live motor B current sensor readings and booster status for an implausible or out-of-range signal.
- Inspect the motor B current sensor connector, wiring, and mounting for looseness, corrosion, damage, or poor contact.
- Check the sensor supply, ground, and signal circuit against the manufacturer's specification while monitoring for intermittent changes.
- Compare the sensor reading with booster motor operation during the specified test to identify sensor drift or an actual motor current problem.
- If wiring and sensor mounting are sound, test the current sensor and booster control module using the manufacturer's diagnostic procedure.
Common fixes
- Repair a loose, corroded, or damaged motor B sensor connection.
- Repair open, shorted, or high-resistance wiring in the current sensor circuit.
- Secure or replace the sensor if its mounting is loose or its signal drifts outside specification.
- Replace the booster motor or control module only when tests confirm the sensor is reporting correctly but the underlying system is faulty.
Can I keep driving?
Power-assisted braking may be reduced or lost, making the pedal harder to press and increasing stopping distance. Do not continue driving if assist is reduced; 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.