What it means
Brake booster motor B is not operating within the expected range. This may reduce brake assist and trigger brake-system warnings.
At a glance
- Usually lights the ABS or stability-control warning light
- The engine or gearbox may go into limp mode
How it works
Brake booster motor B provides electric assistance to the braking system. The control module monitors motor B's operation and sets this performance code when its response is outside the expected range, which can reduce brake assistance.
Common causes
Most likely first.
- Brake booster motor B worn or faulty
- Damaged wiring or poor connection
- Low or unstable system voltage
- Brake booster mechanism binding
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
How to diagnose it
- Record freeze-frame data and scan the brake, ABS, and stability systems for related motor, voltage, or booster codes.
- Check battery and charging-system performance against the manufacturer's specification because low or unstable voltage can affect motor B.
- Inspect motor B's connector and harness for damage, corrosion, loose terminals, or signs of overheating.
- Check the booster mechanism for binding or obstruction using the manufacturer's inspection procedure.
- Use a scan tool to command motor B if supported and compare its operation and circuit readings with the manufacturer's specification.
- If supply, wiring, and mechanism are sound, test motor B and the control-module output before replacing parts.
Common fixes
- Correct weak battery or charging-system performance.
- Repair damaged wiring or clean and secure motor B's connector.
- Correct a binding booster mechanism.
- Replace brake booster motor B if it fails the specified performance test.
- Repair the control module only if its output is confirmed faulty.
Can I keep driving?
Brake assist may be reduced, so the pedal may require more effort and stopping distances may increase. Avoid driving if braking feels abnormal; otherwise drive slowly to a safe place for prompt inspection.
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.