P0A78 on 2012-2019 Toyota Prius C — Drive Motor A Inverter Over-Temperature
1 vehicles · 1 makes · $200-$600 repair
Most Reported On
P0A78 is an OBD-II diagnostic trouble code meaning “Drive Motor A Inverter Over-Temperature.” P0A78 is a hybrid/electric-vehicle code indicating that drive motor 'A' inverter has overheated. The inverter converts the high-voltage battery's DC power into AC to drive the electric traction motor, and it has temperature sensors; when the inverter temperature exceeds safe limits, the control module sets this code and usually reduces power to protect the components. Symptoms include reduced power (limp mode), warning lights, or in severe cases the vehicle refusing to drive. It points to an inverter cooling or electronics problem in the high-voltage drive system rather than the gasoline engine. This code is most commonly reported on 2012-2019 Toyota Prius C, with repair costs ranging from $200 to $600.
Common Causes
Typical Repair Cost
Based on 1 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0A78, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
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FAQ
What does P0A78 mean?
P0A78 stands for "Drive Motor A Inverter Over-Temperature." P0A78 is a hybrid/electric-vehicle code indicating that drive motor 'A' inverter has overheated. The inverter converts the high-voltage battery's DC power into AC to drive the electric traction motor, and it has temperature sensors; when the inverter temperature exceeds safe limits, the control module sets this code and usually reduces power to protect the components. Symptoms include reduced power (limp mode), warning lights, or in severe cases the vehicle refusing to drive. It points to an inverter cooling or electronics problem in the high-voltage drive system rather than the gasoline engine.
What are the most common causes of P0A78?
The most common causes of P0A78 are: Low coolant or air in the inverter cooling loop, Failed inverter/electronics coolant pump, Clogged or restricted inverter cooling passages/radiator, Faulty inverter temperature sensor, Failed or degrading inverter/power module, Cooling fan or thermostat fault in the inverter loop, Excessive load or related high-voltage system fault. The specific cause varies by vehicle.
How much does it cost to fix P0A78?
Repair costs for P0A78 range from $200 to $600, depending on the vehicle and root cause.
Which vehicles are affected by P0A78?
Au7o has documented P0A78 across 1 vehicle models from 1 manufacturers: Toyota.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.