Drivers who encounter a C0593 fault typically notice the brake‑assist warning lamp illuminate on the instrument cluster. The brake pedal feels unusually firm, requiring noticeably more force to achieve the same stopping distance. In many cases the ABS or ESC system will flash a warning and temporarily limit its functions, resulting in a “limp‑mode” that lengthens stopping distances, especially at low speeds. These signs appear suddenly and may worsen if the underlying condition is left unchecked, making early detection essential for safety.
The module that drives the three‑phase brushless motor monitors current in the U‑V‑W windings. Internal circuitry failure, solder joint fatigue, or corrupted firmware can cause the module to read low current on Phase B, triggering C0593.
Corroded connectors, broken pins, or high‑resistance ground paths in the harness that supplies power to the motor can reduce measured current. A short to ground on Phase B will produce the same diagnostic result as a module fault.
Physical damage to the motor windings—often from moisture intrusion or overheating—lowers the current that the module detects. A shorted or open winding on Phase B will register as “low current.”
Out‑of‑date control‑module firmware or an incorrect calibration file may misinterpret normal current levels as low, especially after a major vehicle software update.
– Connect a manufacturer‑approved scan tool. Record all related codes (e.g., ABS, ESC) before clearing C0593.
– Access the brake‑booster motor current readings. Verify that Phase B current is below the manufacturer’s threshold (typically < 0.5 A). Compare with Phases U and W.
– Using a digital multimeter, measure voltage at the motor connector with the brake pedal depressed. Confirm that supply voltage matches specifications (usually 12 V ± 0.5 V).
– Perform a resistance test on each phase winding; values outside the 0.5–1.5 Ω range indicate winding damage.
– Visually inspect the harness for corrosion, pinched wires, or broken clips. Apply dielectric grease to connectors and re‑torque to spec.
– Run the scan tool’s “module communication” routine. A failed handshake points to a defective control module rather than wiring.
– If the module passes hardware tests, update its firmware to the latest version and re‑calibrate the brake‑assist parameters. Clear the code and perform a road test.
– When hardware diagnostics confirm a faulty motor, motor‑control module, or irreparable wiring, replace the defective part. Ensure the replacement unit is VIN‑matched and pre‑programmed to the vehicle’s software version.
Cost Estimates
If the motor‑control module fails the communication test, shows internal voltage irregularities, or repeatedly triggers C0593 after firmware updates, replacement is the most reliable solution. Repairing a damaged board often provides only a temporary fix, especially when moisture or thermal stress has compromised the circuitry.
Flagship One specializes in VIN‑matched control modules, providing a plug‑and‑drive solution backed by warranty. Modern control modules are complex and integrated with safety systems; correct programming and compatibility are essential. Flagship One’s pre‑programmed units ensure the module communicates flawlessly with the brake‑assist, ABS, and ESC networks, eliminating the guesswork of aftermarket re‑coding.
Service Recommendation: Most issues related to this fault are diagnosed and corrected through inspection, wiring repair, and calibration rather than module replacement. For modules not typically replaced through aftermarket suppliers, diagnosis and repair should be performed by a certified automotive technician with access to factory service information and tooling.