P0A78 on Chevrolet
Drive Motor A Inverter Over-Temperature
P0A78 on Chevrolet vehicles indicates drive motor a inverter over-temperature. Au7o has documented this code across 1 Chevrolet model — most commonly on Bolt EUV. 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. Typical repair costs on Chevrolet range from $600 to $1,800, depending on the specific model and root cause.
Common Causes of P0A78
- •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
P0A78 on Chevrolet by Model
Chevrolet Bolt EUV(1 issue)
- Complete loss of propulsion from a spread terminal at the drive unit X2 harness connector (DTC P0A3F / P1B03)2022-2023
GM TSB 19-NA-220, revised February 2023, explicitly covers 2022-2023 Chevrolet Bolt EUV. Customers experience an outright loss of propulsion - the car stops driving - and history codes P0A3F and sometimes P1B03 are stored in the Hybrid/EV Powertrain Control Module. The vehicle often operates normally again after a restart, which makes it dangerous and hard to catch. The cause is a spread (splayed) terminal at harness connection X2 on the T12 transmission/drive unit assembly, where terminals were not perfectly aligned during installation at the assembly plant. GM warns that terminals need not show visible damage to set the codes. Because these are resolver (motor position sensor) circuits, this is a genuine drive-unit interface failure, not a software trip, and it can drop propulsion at speed.
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View P0A78 across all makes →Frequently Asked Questions
What does P0A78 mean on Chevrolet?▼
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. On Chevrolet specifically, this code is documented across 1 model.
What causes P0A78 on Chevrolet vehicles?▼
Common causes on Chevrolet: 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. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0A78 on a Chevrolet?▼
Repair costs on Chevrolet range from $600 to $1,800, depending on the specific model and root cause.
Which Chevrolet models have P0A78 documented?▼
Au7o has documented P0A78 on 1 Chevrolet model: Bolt EUV.