Chassis, generic

C0585 Brake Booster Motor B Phase U-V-W Circuit High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C0585 stands for a phase of booster motor B reading too high, for instance a lead shorted to battery positive or an upper transistor stuck on. The number had another use on older GM-platform cars: on the 2011 Saab 9-5 it identified the left rear damper actuator of the adaptive suspension. In its booster meaning no manufacturer publishes it. The checks required mirror those for C0581 on side A – offline short-to-supply tests and drain-source voltage monitoring as in TI's DRV3245Q-Q1. Redundant drives then isolate the faulty side: Kollmorgen's early patent on redundant windings already shared the torque among the healthy winding sets, and in the Hyundai Mobis design the remaining power module takes over the whole current command.

Likely causes

Phase lead of side B shorted to battery voltage
Upper transistor of power module B shorted or stuck on
Code read on an older GM-platform vehicle where C0585 belongs to a damper actuator

Symptoms

  • Brake system warning lamp
  • Reduced or switched-off electric assist

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–2,800
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

brake booster motor bmotor phase wiring

Related codes

C0583C0584C0586C0581

References: saabwisonline.com, ti.com, patents.google.com, patents.google.com.