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DTC codes / C05xx · Brakes, steering and suspension / C0592

C0592Brake Booster Motor B Phase U-V-W Current High

C0592 indicates that the brake booster motor's three-phase winding (U, V, and W phases) is drawing more current than the control module expects during operation. The module monitors current flow to the motor and sets this code when the measured current exceeds a calibrated threshold, typically due to a shorted winding, a binding mechanical fault, or a wiring issue.

SystemChassis
Code typeGeneric (all makes)
SeverityHigh
Fix difficultyProfessional
AreaBrakes, steering and suspension

Symptoms you may notice

  • Illumination of the brake system warning light or traction control light
  • Reduced or absent power brake assist, requiring harder pedal effort
  • A humming or whining noise from the brake booster area when the brake pedal is pressed
  • The brake pedal may feel stiff or unresponsive during the first few presses
  • Often no symptoms besides the warning light, especially if the fault is intermittent

Common causes, most likely first

  1. Shorted or partially shorted brake booster motor windings (U, V, or W phase)
  2. Mechanical binding or seizure in the brake booster motor or pump assembly
  3. Damaged or chafed wiring between the brake booster motor and the control module
  4. Corroded or loose electrical connectors at the motor or module
  5. Internal fault in the brake booster control module causing excessive current command
  6. Debris or contamination in the brake booster motor causing increased friction

How to diagnose and fix it

  1. Inspect the brake booster motor wiring harness for chafing, corrosion, or loose connectors and repair as needed
  2. Measure the resistance of each motor phase (U, V, W) to ground and between phases to check for shorts or opens
  3. Perform a current draw test on the brake booster motor circuit to confirm excessive current under load
  4. Check for mechanical binding by manually rotating the motor or pump (if accessible) and listening for abnormal noise
  5. Compare live data for brake booster motor current against the manufacturer's specification during activation
  6. Replace the brake booster motor assembly if winding resistance or current draw is out of specification
  7. Reprogram or replace the brake booster control module if it is commanding excessive current without a motor fault

When the motor is not the real culprit

  • A weak or failing battery or charging system can cause the control module to see abnormal current spikes, so always verify system voltage first.
  • The code can be set by a intermittent wiring fault that only appears under vibration, so wiggle-test the harness while monitoring live data.
  • A binding brake booster pump or contaminated brake fluid can increase motor load and set this code without any electrical fault in the motor itself.
  • Some vehicles require a calibration or learn procedure after motor replacement, and skipping it can cause the code to return immediately.
  • Do not overlook the ground connection for the brake booster motor; a poor ground can mimic a shorted winding by skewing current measurements.

Can I keep driving with C0592?

If the brake pedal feels normal and the warning light is the only symptom, you may drive cautiously to a repair shop, but avoid heavy braking or long trips. If power assist is reduced or the pedal is stiff, stop driving and have the vehicle towed, as braking performance is compromised.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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