Chassis, generic

C05AF Brake Booster Motor B Current Sensor Circuit Range/Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C05AF is the plausibility check of the current measurement on booster side B, the second motor or winding system. No manufacturer publishes it. A separate sensing chain for B is needed wherever each power module controls its own winding, as in the Hyundai Mobis dual-winding booster motor, since every module must know its phase currents to regulate torque and to judge its own health. Typical checks run at start-up, before current flows: the controller shorts the amplifier inputs (TI's DRV8343-Q1 offers a pin for this), records the zero point and rejects values outside a band. GM's counterpart for side A, C0596, additionally injects test offsets. A failed B measurement normally leads to side B being switched off and assist relying on side A, possibly with lower power.

Likely causes

Faulty current sense amplifier of side B
Zero offset of side B outside its allowed band
Damaged shunt or solder joint in power module B

Symptoms

  • Brake assist or brake system warning
  • Possibly weaker assist under hard braking

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 b current sensorbrake system control module

Related codes

C0596C0592C0593

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