P0C08: Drive Motor B Phase U-V-W Circuit/Open

What it means

The drive motor B phase U-V-W output reports a circuit/open condition. The drive motor's position, current and temperature are watched continuously; a fault here downgrades the inverter to a safe operating point or triggers torque reduction.

At a glance

• Usually lights the check-engine light
• The engine or gearbox may go into limp mode

How it works

Drive Motor B's three phase connections, U, V, and W, carry inverter-controlled current that turns the motor. P0C08 sets when the control module detects an open in Drive Motor B's phase path, which can be caused by a broken wire, an open winding, or a connector pin pushed back out of place.

Common causes

Most likely first.

1. Open phase wire
2. Open motor winding
3. Pin pushed back out of connector body

Symptoms

• EV/hybrid system warning light on
• Reduced motor power or torque
• Possible limp mode or vehicle shutdown

How to diagnose it

1. Read freeze-frame and live hybrid data for Drive Motor B phase or current faults, torque request, and speed to understand when the open is detected.
2. Check for companion Drive Motor B inverter or phase codes that may narrow the fault to a particular part of the system.
3. With the high-voltage system disabled as directed by the manufacturer, inspect the U, V, and W connectors for pushed-back pins, loose fit, corrosion, or harness damage.
4. Have a qualified technician test continuity in the Drive Motor B phase wiring and motor windings using the manufacturer's isolation procedure.
5. If the phase wires and windings pass, check the inverter's Drive Motor B phase output using the manufacturer's diagnostic procedure.

Common fixes

• Reseat or replace a phase connector terminal that has backed out.
• Repair an open in the Drive Motor B phase harness.
• Repair or replace the motor if an open winding is verified.
• Repair or replace the inverter if its phase output is confirmed faulty.

Can I keep driving?

Avoid driving when Drive Motor B torque is reduced or inconsistent; the vehicle may further limit power or shut down. Have the fault assessed before a long trip, and stop safely if propulsion becomes unreliable.