P0C79 — Drive Motor "A" Inverter Voltage Too High

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

  1. Read the code and freeze frame Connect an OBD2 scanner, confirm P0C79 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
  3. Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the drive motor "A" inverter voltage too high for damage, corrosion, chafing or poor contact.
  4. Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
  5. Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
  6. Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P0C79 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P0C79 (parts and labor, USD, independent shop rates): Control module repair: $300–$1,000; Repair wiring or connectors: $80–$250; Replace the faulty sensor or actuator: $150–$500. Overall, fixing P0C79 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

Will P0C79 clear itself?

Sometimes P0C79 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

How much does it cost to fix P0C79?

Control module repair — $300–$1,000; Repair wiring or connectors — $80–$250; Replace the faulty sensor or actuator — $150–$500. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Is it safe to drive with P0C79?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How do I diagnose P0C79 myself?

Start with a scan: confirm P0C79, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the sensor and actuator circuits, and verify the suspect component against live data before buying parts.

What are the symptoms of P0C79?

Drivers most often notice: increased fuel consumption in some cases, the affected system operates intermittently or not at all, Check Engine Light on, possible limp mode depending on the affected component.

When your hybrid or plug-in hybrid vehicle logs OBD2 code P0C79, it means the inverter managing drive motor "A" has detected voltage exceeding safe limits. The inverter acts as a power converter between the high-voltage battery pack and the electric motor — it transforms DC to AC for propulsion and AC back to DC during regenerative braking. If that voltage climbs past what the control module expects, the system flags P0C79 and illuminates the check engine or hybrid warning light.

The powertrain control unit sets P0C79 after monitoring the inverter's voltage feedback circuits against pre-calibrated thresholds. Typically, the fault must appear consistently across multiple drive cycles before the light comes on. When the code triggers, the ECU saves a freeze-frame snapshot — engine speed, load, coolant temperature, and vehicle speed captured at the exact moment of the fault. Reviewing that snapshot first gives you the best starting point for diagnosis.

Common Symptoms of P0C79

  • Check Engine Light or hybrid system warning lamp is illuminated
  • Electric drive mode may be disabled or operate only inlimp-home mode
  • Reduced acceleration and overall power output compared to normal
  • Higher fuel consumption because the engine compensates for lost electric assist
  • Intermittent or complete loss of electric motor function
  • Possible stalling or failure to start, particularly in severe over-voltage conditions

What Causes P0C79

Most failures trace back to wiring and connectors before the expensive components fail:

  • Damaged, chafed, or broken wiring in the inverter circuit
  • Corroded, loose, or bent pins at the inverter or motor connectors
  • Blown fuse feeding the inverter high-voltage supply
  • Weak or corroded ground connection at the inverter housing
  • Faulty drive motor inverter internally shorting or failing
  • Malfunctioning voltage sensor or related control module

How to Diagnose P0C79

  1. Connect an OBD2 scanner, record all stored codes, and save the freeze-frame data — these conditions are critical when you retest later.
  2. Review any accompanying diagnostic trouble codes. Search NHTSA and your manufacturer's database for TSBs related to P0C79 or inverter voltage issues on your specific model.
  3. Perform a hands-on inspection of the inverter harness and connectors. Look for cracked insulation, corrosion buildup, moisture intrusion, and any wires pulled loose from their terminals.
  4. Use a multimeter to verify reference voltage, ground integrity, and signal continuity at the inverter and motor connectors against factory specifications.
  5. While observing live data on the scanner, gently wiggle the harness — voltage dropouts or signal interruptions point to broken conductors hidden inside the insulation.
  6. Clear the code, drive through the freeze-frame conditions, and confirm P0C79 does not return.

Repair Options for P0C79

  • Wiring harness repair or connector replacement: $80–$250
  • Drive motor inverter assembly replacement (new or remanufactured): $300–$1,000
  • Associated voltage sensor or ground repair: $150–$500

Total Repair Cost

Most shops charge between $80 and $1,000 to resolve P0C79, depending on the root cause. Wire and connector issues cluster at the low end, while inverter replacement drives costs to the upper limit. An accurate diagnosis before purchasing parts is the smartest move — the most expensive fix is rarely the first one to investigate.

Can You Drive With P0C79?

The vehicle typically remains drivable in gasoline-only mode, but with noticeably diminished performance and reduced fuel economy. If you experience stalling, a no-start condition, or warning lights related to braking or steering assist, treat the situation as urgent and have the vehicle transported to a repair facility.

Related OBD2 Codes