Chassis, generic

C0596 Brake Booster Motor A Current Sensor Circuit Range/Performance

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C0596 questions the current measurement of booster motor A itself rather than the motor. GM's 2016/2019 hybrid booster tests its overcurrent comparator at start-up by forcing minimum and maximum PWM and reading the comparator output back over a feedback line, while the voltage behind the master switch must sit near zero or near battery voltage; a hardware overcurrent flag on that line during operation also sets it (30 ms). GM's 2019 IBC unit injects zero, positive, negative and common-mode offsets into the current sense path at power-up, with the motor almost still and 7.1–18 V supply, and compares the results with their allowed bands. All Type A with MIL. Driver chips such as TI's DRV8343-Q1 short the amplifier inputs on command for this zero calibration.

Likely causes

Faulty current sense amplifier or motor driver chip
Overcurrent comparator or its feedback line not responding
Supply voltage outside the test window during start-up

Symptoms

  • Brake assist warning right after switching on
  • Heavy brake pedal, check engine lamp on

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€200–3,000
Time0.5–4 h

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

Parts involved

booster motor a current sensorbrake system control module

Related codes

C05AFC0590C0591C0595

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