OBD-II Code P0A93
Inverter Cooling System Performance
P0A93 is an inverter cooling system fault — not a direct battery capacity code, but one that often appears in combination with battery faults and is important not to ignore. Toyota's hybrid inverter converts DC power from the HV battery to three-phase AC for the motor-generators and vice versa during regenerative braking. This process generates significant heat, requiring a dedicated liquid cooling circuit separate from the engine cooling system. The inverter cooling circuit uses its own electric pump, reservoir, and heat exchanger. P0A93 is stored when the inverter temperature sensor detects inadequate cooling — typically because the inverter cooling pump has failed or is weak, coolant level is low, or the system has an air pocket restricting flow.
At a Glance
Fault Code
P0A93
Affects
Prius Gen 2 (2010–2015), Prius Gen 3 (2016–2023), Camry Hybrid, Highlander Hybrid & more
Can You Drive?
Drive with caution
Typical Cost (BC)
Cooling pump replacement: $400–$700 · Sensor only: $200–$350
What Causes P0A93?
- 1Inverter coolant pump failure — the most common cause, pump impeller degrades with age
- 2Inverter coolant level low — small leak in inverter cooling circuit
- 3Air pocket in inverter cooling circuit — inadequate bleeding during coolant service
- 4Inverter cooling pump relay failure
- 5Clogged inverter coolant passages from scale buildup in older vehicles
- 6Inverter temperature sensor fault — falsely reading high temperature
Symptoms You May Notice
- Check engine light with P0A93 stored
- Vehicle may enter reduced-power mode when inverter approaches thermal limit
- In severe cases, vehicle may refuse to start until inverter temperature normalises
- No dramatic driver-perceived symptoms in early pump failure — the fault often appears before performance is noticeably affected
- In hot weather or during heavy use (highway, towing), symptoms worsen
Can You Drive with P0A93? — Drive with caution
With P0A93 alone, the vehicle is typically driveable but should be driven conservatively — avoid extended highway driving, aggressive acceleration, or towing until the cooling issue is resolved. Driving with inadequate inverter cooling risks permanently damaging the inverter ($2,000–$4,000 to replace), which is a far more expensive repair than the cooling pump. If P0A93 appears alongside battery fault codes, address the cooling issue first or simultaneously.
How It's Diagnosed
- 1
OBD-II scan to confirm P0A93 and identify any accompanying codes
- 2
Inverter coolant level check — check inverter reservoir, not the engine coolant reservoir (they are separate)
- 3
Inverter cooling pump operation test — verify pump runs and produces adequate flow
- 4
Coolant temperature comparison between inverter inlet and outlet under load
- 5
Visual inspection for coolant leaks at inverter connections and reservoir
How It's Fixed
The most common fix for P0A93 is inverter cooling pump replacement — the electric pump that circulates coolant through the inverter circuit. In Gen 2 and Gen 3 Prius, this pump typically fails between 120,000–200,000 km. The replacement pump is an OEM or equivalent part and the job typically takes 1–2 hours including coolant flush and bleed. If coolant level was low due to a slow leak, the leak source must also be identified and repaired. If the inverter temperature sensor itself is faulty, sensor replacement resolves the code without a pump change.
Typical cost in BC
Cooling pump replacement: $400–$700 · Sensor only: $200–$350
Prices include parts and labour. Contact us for a firm quote on your specific vehicle.
Vehicles Affected by P0A93
Frequently Asked Questions — P0A93
The inverter cooling system has its own separate reservoir — typically a small white translucent tank near the inverter, distinct from the main engine coolant reservoir. Many drivers check the engine coolant and find it full, not realising the inverter has a completely separate circuit. Check the inverter coolant reservoir specifically.
Indirectly, yes. Excessive inverter heat can affect the thermal management of the battery system in vehicles where cooling circuits are closely integrated. More critically, a failed inverter from thermal damage will disable the entire hybrid drivetrain. The inverter is a significantly more expensive component than the cooling pump, so addressing P0A93 promptly is strongly recommended.
The inverter cooling system uses the same type of coolant (ethylene glycol based) but operates as a completely separate, sealed circuit with its own pump, reservoir, and heat exchanger. It does not mix with the engine cooling circuit. When performing a coolant flush on a Toyota hybrid, both circuits must be serviced separately.
Related Fault Codes
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