Powertrain, generic · Hybrid propulsion

P0C0A Drive Motor B Phase U-V-W Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0C0A reports that a phase line of drive motor B reads too high, typically a short to the positive high-voltage rail or a high-side power switch that stays on. It mirrors P0C07 for motor A and completes the motor B trio with P0C08 (open) and P0C09 (low). No manufacturer documents P0C0A publicly; GM only uses P0C08 for motor B phase circuits, based on missing phase current. CARB requires hybrid components to be monitored for circuit faults. A phase stuck high leads to uncontrolled current, so the inverter switches motor B off immediately and P0C04 may be stored as well. For the driver this means a warning lamp, reduced propulsion and, on electric all-wheel drive, loss of the driven axle.

Likely causes

Shorted high-side power switch in the motor B inverter
Phase cable of motor B shorted to the positive high-voltage path
Faulty gate driver holding a switch on

Symptoms

  • Immediate shutdown of motor B with warning lamp
  • Reduced performance or loss of electric all-wheel drive

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€200–6,000
Time1–10 h

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

Parts involved

drive motor b phase uvwdrive motor b inverter

Related codes

P0C08P0C09P0C07P0C04P0BFE

References: law.cornell.edu, gsi.ext.gm.com.