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

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.

Symptoms

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

Most 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

What to check, in order

Start with the simplest. You can tick off each step.

1. Read the codes with a hybrid-compatible scanner and write down the freeze frame data
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Make sure the battery cooling air intake is clean
4. Check the 12 V auxiliary battery, which can also trigger warnings
5. Leave any high-voltage measurements to a specialized repair shop

Good to know

• It can trigger limp mode.
• It affects emissions.

What each character of P0C0A means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• C: Subsystem depends on the code range
• 0A: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0C0A?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0C0A?

The most common causes are: 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.

Related codes

• P0C08Drive Motor B Phase U-V-W Circuit/Open
• P0C09Drive Motor B Phase U-V-W Circuit Low
• P0C07Drive Motor A Phase U-V-W Circuit High
• P0C04Drive Motor B Current High
• P0BFEDrive Motor B Phase U-V-W Current Sensor Correlation

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 12OBDG06 Hybrid Diagnostics

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.