What Does P0C79 Mean?
DTC P0C79 indicates that the inverter voltage for drive motor A has exceeded the maximum allowable threshold. The inverter converts DC battery voltage to AC for the electric motor, and an overvoltage condition can result from regenerative braking energy, a failing voltage regulator, or a fault in the DC bus voltage management. This is a serious condition that can damage power electronics.
Safety Warning
Inverter overvoltage can destroy IGBT/MOSFET switching devices, causing sudden loss of propulsion or uncontrolled motor behavior. The vehicle should immediately limit power and may shut down the electric drivetrain to prevent catastrophic inverter failure.
Common Causes
30%
Excessive regenerative braking energy not being properly absorbed by the battery or resistor
25%
Inverter DC bus voltage regulation fault (failed voltage clamping circuit)
20%
Battery pack at or near full state of charge refusing regenerative energy
15%
Faulty inverter voltage sensor providing incorrect readings
10%
Wiring fault causing voltage spikes on the DC bus
Diagnostic Steps
1
Review freeze frame data to identify the actual inverter voltage at the time of fault and the vehicle operating conditions (deceleration, speed, battery SOC).
2
Monitor the inverter DC bus voltage in real time during a test drive, paying close attention during regenerative braking events.
3
Check the battery state of charge and verify the BMS is properly accepting regenerative energy; a near-full battery will reject regen energy causing voltage spikes.
4
Inspect the inverter voltage clamping circuit and associated components for proper operation.
5
Test the inverter voltage sensor by comparing its reading to an external HV voltmeter measurement on the DC bus.
6
Inspect HV bus connections for loose or corroded terminals that could cause transient voltage spikes.
Estimated Repair Cost
$500 - $4,000
Parts + labor, varies by vehicle and location
DTC P0C79 indicates that the inverter voltage for drive motor A has exceeded the maximum allowable threshold. The inverter converts DC battery voltage to AC for the electric motor, and an overvoltage condition can result from regenerative braking energy, a failing voltage regulator, or a fault in th...
The most common cause of P0C79 (Drive Motor "A" Inverter Voltage Too High) is: Excessive regenerative braking energy not being properly absorbed by the battery or resistor
Typical repair costs for P0C79 range from $500 to $4,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Inverter overvoltage can destroy IGBT/MOSFET switching devices, causing sudden loss of propulsion or uncontrolled motor behavior. The vehicle should immediately limit power and may shut down the electric drivetrain to prevent catastrophic inverter failure.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0C79 to identify the root cause.
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Quick Info
Category
Powertrain
System
Drive Motor A Inverter / Power Electronics
Difficulty
Type
Generic (SAE)
Recommended Tools
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