A failing or degraded coolant pump that reduces flow through the inverter cooling circuit.; Low coolant level or trapped air in the inverter cooling loop, often after service or a slow leak.; A blocked or clogged inverter radiator or cooling fins packed with debris.; A faulty inverter temperature sensor that reports a higher temperature than actual.; A stuck or inoperative cooling fan that prevents airflow over the inverter heat sink.; Internal inverter degradation, such as failing power modules or thermal paste breakdown, causing excessive heat generation.; Wiring damage or corrosion in the temperature sensor circuit, leading to an erratic or biased signal.

DTC codes / P0Cxx · Hybrid propulsion / P0C12

P0C12Drive Motor A Inverter Phase V Over Temperature

Q: What does code P0C12 mean?

Drive Motor A Inverter Phase V Over Temperature. P0C12 indicates that the inverter for drive motor A has reported an over-temperature condition on its phase V output circuit, meaning the power electronics that convert direct current (DC) battery voltage into three-phase alternating current (AC) for the motor are running hotter than the manufacturer's safe limit. The computer detects this through a temperature sensor inside the inverter and sets the code when the reading exceeds a calibrated threshold for a set time, often triggering a power reduction to protect the hardware.

P0C12 indicates that the inverter for drive motor A has reported an over-temperature condition on its phase V output circuit, meaning the power electronics that convert direct current (DC) battery voltage into three-phase alternating current (AC) for the motor are running hotter than the manufacturer's safe limit. The computer detects this through a temperature sensor inside the inverter and sets the code when the reading exceeds a calibrated threshold for a set time, often triggering a power reduction to protect the hardware.

SystemPowertrain

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light or a dedicated hybrid/EV warning lamp, often with no other noticeable symptoms at first.
Reduced propulsion power or a limp-home mode that limits vehicle speed and acceleration.
The vehicle may refuse to start or shift into gear if the inverter temperature is still above the safe threshold.
Intermittent power loss during sustained high-load driving, such as climbing a long grade or towing.
A burning or hot-electronics smell from the inverter area in severe cases, though this is less common.
Audible cooling fan operation that continues after the vehicle is shut off, as the system tries to cool the inverter.

Common causes, most likely first

A failing or degraded coolant pump that reduces flow through the inverter cooling circuit.
Low coolant level or trapped air in the inverter cooling loop, often after service or a slow leak.
A blocked or clogged inverter radiator or cooling fins packed with debris.
A faulty inverter temperature sensor that reports a higher temperature than actual.
A stuck or inoperative cooling fan that prevents airflow over the inverter heat sink.
Internal inverter degradation, such as failing power modules or thermal paste breakdown, causing excessive heat generation.
Wiring damage or corrosion in the temperature sensor circuit, leading to an erratic or biased signal.

How to diagnose and fix it

Scan all modules for stored and pending codes, and record freeze-frame data to see the conditions when P0C12 set.
Check the inverter coolant level and condition, and pressure-test the cooling system for leaks or air pockets.
Verify that the inverter coolant pump runs with the key on and that flow is visible in the reservoir or service port.
Inspect the inverter radiator and cooling fan for obstructions, and confirm the fan operates when commanded.
Measure the resistance and signal voltage of the inverter temperature sensor circuit, comparing to manufacturer specifications.
Use a scan tool to monitor live inverter temperature data while the vehicle is running and compare it to actual surface temperature readings with an infrared thermometer.
If all external cooling and sensor circuits check out, follow the manufacturer's diagnostic flow for internal inverter faults, which may require inverter replacement or repair.

Cooling system faults mimic inverter failure

A significant number of P0C12 cases are caused by a weak coolant pump or a low coolant level rather than a failed inverter, so always verify coolant flow before condemning the power electronics.
Air trapped in the inverter cooling loop after a coolant service can create hot spots that trigger the code even when the coolant level appears correct, so proper bleeding is essential.
The inverter temperature sensor circuit can be affected by corrosion at connectors, and a biased signal may set P0C12 without any actual overheating.
Some vehicles will set P0C12 as a history code after a brief overheating event and will not command a power reduction unless the fault is active, so clearing the code and test-driving may be appropriate after repairs.
The code does not always mean the inverter is internally damaged; external cooling system components, such as the radiator fan or pump, are common root causes that are often overlooked.

Can I keep driving with P0C12?

Do not continue driving with an active P0C12, because continued operation can overheat and permanently damage the inverter, leading to a costly repair. If the light is on but the vehicle drives normally, limit driving to a short distance to a repair facility and avoid heavy acceleration or sustained high loads.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.