C0595 is a chassis diagnostic code indicating the brake booster's internal power driver circuit is experiencing a range or performance issue. This typically relates to an electric brake booster system (common in many modern vehicles) where the electronic control module that drives the booster motor has detected a fault in its output stage. The brake booster provides power-assisted braking, and this code suggests the electronic driver circuitry is outside normal operating parameters.
The electric motor or pump within the brake booster assembly has failed or is drawing excessive current, causing the internal driver to detect a fault condition.
The pressure sensor that monitors brake booster vacuum or pressure has failed, causing the control module to report a range/performance issue.
Damaged wiring, corroded connectors, or poor electrical connections between the brake booster and control module can cause signal or power irregularities.
The internal electronic driver circuitry within the brake booster assembly itself has failed, though this is less common than other causes.
A blown fuse or failed relay that supplies power to the brake booster system can cause the driver to detect a fault.
In rare cases where the brake booster is externally controlled, the vehicle's chassis or powertrain module may have a fault, though this is the least likely cause.
Driving is not recommended when this code is active, as the brake booster may not provide power assist. You should have the vehicle towed or repaired before driving, as stopping distances will increase and braking will require significantly more pedal effort.
Costs vary significantly by vehicle make and model. A brake booster assembly with an integrated motor can range from $300 to over $1,000 for parts alone, plus labor. Minor issues like fuses, relays, or wiring repairs are considerably less expensive.
No, they are separate components. The brake booster (power brake unit) uses vacuum or electric assistance to reduce pedal effort, while the master cylinder converts pedal force into hydraulic pressure. Some newer vehicles combine them into a single assembly, but they serve distinct functions.
No. While the PCM/ECM could theoretically cause this code in some vehicle designs, it is extremely rare and should be considered only after all other causes (motor, sensor, wiring, connectors, fuses) have been definitively ruled out. The brake booster assembly itself is the cause in the vast majority of cases.