P0A3C: Drive Motor A Inverter Over Temperature
What to do
If drive cuts out and returns after the car cools, suspect this loop's circulation. Ask specifically whether the inverter's own coolant loop — separate from the engine's — has been checked: level, pump running, no air. It is a five-minute check and the commonest fix, and it is skipped whenever someone assumes the engine's coolant bottle speaks for the whole car.
What this code means
The power stage driving the main motor got too hot — the inverter's own protection threshold was crossed.
The inverter has its own cooling system, and that fact is most of this diagnosis. On the majority of hybrids the power electronics run a separate low-temperature loop with its own pump, its own small radiator and its own reservoir — because the electronics must be kept far cooler than an engine runs. A full engine cooling system therefore proves nothing about this one, and "the coolant is fine" is the misdirection this family lives on. The corpus already carries the loop's own hardware: the pump at P0A05 and its temperature sensing at P0A00 are this system.
The failure story is almost always circulation: an electric pump that stopped, air trapped after work on the system, a level quietly low in a reservoir nobody checks. The inverter derates or shuts down to protect its switches — abruptly, unlike a motor's gradual derate — so the presenting complaint is often a sudden loss of drive that recovers after cooling.
Heat is how inverters die, so repeated excursions are not cosmetic: each one ages the power semiconductors. This code recurring is the cheap warning before P0A78 becomes the expensive conclusion.
Likely causes
Start here
- Faulty inverter coolant pump · moderate
- Low inverter coolant level · easy
Less common
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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