This code indicates the brake booster control module has detected abnormally low electrical current in one or more of the three motor phases (U, V, W) that drive the brake booster vacuum pump or hydraulic assist motor. The condition typically signals an open circuit, high-resistance connection, or internal motor winding failure that prevents the motor from drawing its expected operational current.
The three-phase motor windings inside the brake booster assembly may have an open circuit or high resistance due to wear, overheating, or manufacturing defect, preventing current flow.
The wiring harness connecting the control module to the motor may have a break, corrosion, or pin push-out in the U, V, or W phase circuits, interrupting current delivery.
Poor contact resistance at the motor or control module connectors can create sufficient voltage drop to register as low current, even if the motor and wiring are otherwise intact.
The dedicated module that drives the motor phases may have a failed output driver circuit or internal fault that prevents it from supplying sufficient current to the motor.
A weak battery or charging system fault may cause the control module to detect insufficient current draw because the motor cannot reach its rated operational voltage.
No. This fault indicates the electric brake assist may be inoperative or severely reduced, resulting in a hard brake pedal and significantly increased stopping distances. The vehicle should not be driven until repaired.
Almost never. This code specifically relates to the brake booster motor circuit, which is controlled by a dedicated brake actuator or booster control module, not the engine computer. PCM replacement is almost always an incorrect diagnosis for this fault.
These letters designate the three electrical windings (phases) of the brushless DC motor that drives the brake booster. The control module monitors current in each phase to detect motor malfunctions; low current indicates an open circuit or failure to energize one or more windings.
No. While the symptom of hard braking may feel similar to a vacuum leak, C0593 is an electrical fault detecting low motor current, not a pneumatic leak. The issue is in the motor drive circuit, not the vacuum hoses or brake lines.