P0C79: Drive Motor A Inverter Voltage Too High

P0C79 reports that the DC voltage at the inverter of drive motor A rose above its protection limit. Overvoltage can come from regenerative energy the battery cannot absorb, from a contactor opening under load or a loose high-voltage connection, and it can also be a false reading. In the 2018 Outlander PHEV a hardware comparator in the front motor control unit trips at 370 V; one event with the IGBTs active, or 0.5 s with them shut down, sets the code; after ruling out other voltage codes, the manual checks the torque of the battery cable at the power drive unit. Subaru revised its diagnosis for the 2014-2015 Crosstrek Hybrid (16-114-18), and Audi traces intermittent P0C7900 on the Q4 e-tron to software. Drive motor B uses P0C7A, the generator P0C7B.

Symptoms

• Hybrid or EV warning lamp, electrical system fault message
• Drive system will not activate or shuts down until restarted
• Reduced drive power

Most likely causes

• Battery cable at the inverter loose or not at specified torque
• Inverter or its voltage detection faulty
• Voltage spike from regeneration or a contactor opening under load
• Motor control software, fixed by an update

What to check, in order

Start with the simplest. You can tick off each step.

1. Read the codes with a hybrid-compatible scanner and write down the freeze frame data
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Make sure the battery cooling air intake is clean
4. Check the 12 V auxiliary battery, which can also trigger warnings
5. Leave any high-voltage measurements to a specialized repair shop

Good to know

• It can trigger limp mode.
• It affects emissions.

What each character of P0C79 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• C: Subsystem depends on the code range
• 79: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0C79?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0C79?

The most common causes are: battery cable at the inverter loose or not at specified torque; inverter or its voltage detection faulty; voltage spike from regeneration or a contactor opening under load.

Related codes

• P0C7ADrive Motor B Inverter Voltage Too High
• P0C7BGenerator Inverter Voltage Too High
• P0A78Drive Motor A Inverter Performance
• P0D2EDrive Motor A Inverter Voltage Sensor A Circuit Range/Performance

Sources

• mitsubishitechinfo.com: M154934120004400USA
• static.nhtsa.gov: MC 10143887 9999
• static.nhtsa.gov: MC 11005947 0001
• mitsubishitechinfo.com: N503230090000900USA

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.