What it means
The brake booster controller detected that its internal power driver is not performing as expected. This can affect electric brake assist.
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 brake booster controller uses an internal power driver to control or monitor electric brake assist. C0595 sets when the controller detects that this driver’s operation is outside its expected performance range, which may affect brake assist.
Common causes
Most likely first.
- Power driver internal fault
- 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
- Scan the brake and stability-control modules, record freeze-frame data, and note related voltage, booster, or communication codes before clearing anything.
- Check battery condition and the brake booster controller’s power and ground connections, since low or unstable supply can affect driver performance.
- Inspect the controller and booster connectors and wiring for corrosion, loose terminals, water intrusion, or damage.
- Use a capable scan tool to compare available booster command and feedback data with the manufacturer’s expected behavior.
- If external power, ground, and wiring checks pass, follow the manufacturer’s tests for the internal power driver and controller.
Common fixes
- Clean and secure a poor controller power or ground connection.
- Repair damaged wiring or connector terminals in the brake booster controller circuit.
- Perform the manufacturer-required calibration or software update if specified for this fault.
- Replace the brake booster controller only after its internal driver is confirmed faulty by the prescribed tests.
Can I keep driving?
Because brake assist may be reduced and ABS or stability control may be unavailable, avoid driving until braking assistance is confirmed normal. If the pedal feels unusually hard or braking changes, 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.