Chassis, generic

C0593 Brake Booster Motor B Phase U-V-W Current Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C0593 is meant for a current value on booster side B that is too low or negative where the controller expects about zero or a commanded positive current. It is not documented by any manufacturer; like C0592 it shows up only in GM's old keyword list PIP5094 with a different meaning. Unlike the high fault, a low value rarely reflects real current: more often the measuring chain has an offset. TI's DRV8343-Q1 has a calibration input that shorts the amplifier inputs internally so the controller can store the zero point and subtract it, and a drifted zero leads exactly to such readings. GM's matching test for side A trips below −20 A or −38 A. In a dual-winding motor like the Hyundai Mobis design, module B is then shut down and module A carries the load alone.

Likely causes

Zero point of the side B current measurement drifted
Defective power module B or its driver chip
High resistance in a side B phase connection

Symptoms

  • Brake assist warning message
  • Assist weaker under hard braking if only side A remains

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€200–3,000
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

C0592C0591C05AFC0584

References: ti.com, patents.google.com, static.nhtsa.gov, gsi.ext.gm.com.