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

What it means

The drive motor B phase U-V-W output reports a circuit high 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 inverter switches power through its U, V and W phase paths to turn the motor. The control module monitors the phase output and related motor data; this code sets when the combined U-V-W circuit is detected above its expected electrical range.

Common causes

Most likely first.

1. Phase wire shorted to high voltage
2. Open motor winding
3. Connector pins corroded - high contact resistance

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 data and related hybrid or EV codes to see when the U-V-W fault occurred and whether it followed high load or a temperature change.
2. With the vehicle powered down according to the manufacturer's high-voltage safety procedure, inspect motor B's U, V and W wiring and connectors for damage, contamination or corrosion.
3. Check the phase connector terminals for poor contact, pushed-back pins or corrosion that could raise contact resistance.
4. Have a qualified technician test the U, V and W phase paths for an open winding and check for an unintended connection to a high-voltage source.
5. Compare phase output and motor data with the manufacturer's diagnostic procedure to determine whether the fault is in the wiring, motor winding or inverter.

Common fixes

• Clean or repair corroded motor B phase connector terminals.
• Repair damaged U, V or W phase wiring and restore secure connections.
• Repair or replace the motor B winding if testing confirms it is open.
• Repair the confirmed inverter or high-voltage circuit fault.

Can I keep driving?

Avoid driving if torque is reduced, limp mode is active or the vehicle may shut down; a phase fault can cause loss of drive. Arrange prompt diagnosis, and do not handle high-voltage wiring.