Chassis, generic

C0590 Brake Booster Motor A Phase U-V-W Current High

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C0590 means the current measured in the drive of booster motor A is too high, mostly checked while the bridge is idle and almost nothing should flow. GM uses it in several units, always Type A with MIL: its 2016/2019 hybrid booster trips on leakage current above 20 A for 5 ms, the XT4 module on an idle offset above 36.1 A or a phase current above 200 A, and the 2023/2025 EBCM tables on a shunt offset above 38 A for 0.2 s. In GM's 2019 IBC unit it also flags a bridge driver whose overcurrent detection fails its power-up self-test. Mitsubishi maps C18E1-19 of the Outlander PHEV brake unit to C0590 with MIL after one trip; booster assist, regeneration and automatic braking stop. On the 2011 Saab 9-5 the number was a damper actuator code.

Likely causes

Leaking or partly conducting MOSFET in the booster motor bridge
Shunt or measuring amplifier offset drifted upward
Winding short in booster motor A drawing excess current
Bridge driver chip failing its overcurrent self-test

Symptoms

  • Brake assist warning, much higher pedal effort
  • Check engine, ABS or brake warning lamps on
  • Regenerative braking and automatic brake functions unavailable

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 abrake system control module

Related codes

C0591C0592C0595C0596C057F

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, mitsubishitechinfo.com.