📌 What does the P0A79 code mean?
The P0A79 code indicates a problem detected by the high voltage control ECU (HV ECU) in the inverter current sensor circuit. The inverter plays a crucial role in hybrid vehicles: it converts the direct current (DC) from the high voltage battery into alternating current (AC) to power the MG1 and MG2 electric motors, and vice versa during regenerative braking.
The system relies on several power transistors to switch the energy, and current sensors to monitor the electrical flows in the V and W phase cables. If a fault is detected in the reading from these sensors, the P0A79 code is recorded.
🔍 Possible causes of the P0A79 code:
- Faulty inverter with converter assembly,
- Damaged inverter wiring harness, open or short circuit,
- Poor electrical connection on the inverter circuit,
- Corroded connectors or bent/loose pins.
🚨 Common symptoms:
- Check engine light on (or “Service engine soon” light).
🧰 How to fix the P0A79 code:
- Visually inspect the wiring harness between the inverter and the HV ECU.
- Look for visible damage: worn, cut, or melted cables.
- Check the connectors: ensure no pins are twisted, broken, pushed out, or oxidized.
- Test the continuity and insulation of the circuits with a multimeter.
- If all the wiring appears intact, the problem may come directly from the inverter/converter – this component may require replacement if deemed faulty.
- In some cases, reprogramming or replacing the HV control ECU may be necessary if the integrated sensors are not functioning correctly.
🧠 Good to know:
This code is specific to hybrid vehicles and can appear on models such as the Toyota Prius, Lexus CT200h, or other Toyota/Lexus hybrid vehicles.
It is recommended to use a specialized OBD-II scanner for hybrids to retrieve detailed data from the HV system.