P0C16: Drive Motor B Inverter Phase W Over Temperature

What it means

The inverter phase W of drive motor B reports junction temperature above the protection threshold. Sustained high phase current.

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 battery current through phase W to create motor torque. The hybrid control module monitors the inverter’s phase W junction temperature and sets P0C16 when it exceeds the protection threshold, often after sustained high phase current or inadequate local cooling.

Common causes

Most likely first.

1. Sustained phase overload
2. Local cooling failure

Symptoms

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

How to diagnose it

1. Record freeze-frame data and check live inverter temperature and phase-current data to see whether the overheat follows heavy load or appears immediately.
2. Inspect Drive Motor B’s inverter cooling passages, coolant level, pump operation, and nearby connections for blockage, leaks, or poor circulation.
3. With the high-voltage system made safe according to the manufacturer’s procedure, inspect phase W connections and wiring for damage, looseness, or signs of overheating.
4. Compare phase W current and temperature with phases U and V under the manufacturer’s specified test conditions to identify a local imbalance.
5. If cooling and connections are sound, have the inverter and its temperature sensing checked using the manufacturer’s diagnostic procedure.

Common fixes

• Restore coolant flow by correcting a low coolant level, blockage, or cooling-pump fault.
• Repair a damaged or loose phase W connection or harness.
• Correct a condition causing sustained overload of Drive Motor B.
• Repair or replace the inverter if its phase W switching or temperature sensing has failed.

Can I keep driving?

Avoid hard acceleration, steep climbs, and towing; reduced torque or a shutdown may occur if phase W overheats again. If power drops or a hybrid-system warning appears, stop somewhere safe and arrange assistance.