P0A70 Generator Phase U Current Low

P0A70 Possible Causes

  • Faulty inverter with converter assembly
  • Inverter with converter assembly harness open or shorted
  • Inverter with converter assembly circuit poor electrical connection

What Does It Mean?

How to Fix Code P0A70

Check the “possible causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

P0A70 Possible Symptoms

Illuminated MIL (or service engine soon warning light)

P0A70 Meaning

The inverter converts high voltage DC from the HV battery and AC from MG1/MG2. The inverter contains a three-phase bridge circuit, which consists of 6 power transistors each for MG1 and MG2, to convert DC and three-phase AC.
The HV control ECU controls the operation of the power transistors.

The inverter transmits information necessary to perform control, such as current and voltage, to the HV control ECU.
The motor inverter current sensors detect the current flowing through the V and W phase cables between the inverter and MG1/MG2. The inverter transmits information necessary to perform control, such as current and voltage, to the HV control ECU.
The HV control ECU monitors the inverter current sensors to detect a malfunction in the sensor system.

P0A71 Generator Phase U High Current

P0A71 Possible Causes

  • Faulty inverter with converter assembly
  • Inverter with converter assembly harness open or short-circuited
  • Inverter with converter assembly circuit poor electrical connection

What Does It Mean?

How to Fix Code P0A71

Check the “Possible Causes” listed above. Visually inspect the related cable harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

P0A71 Possible Symptoms

Engine light on (or service engine soon warning light)

P0A71 Meaning

The inverter converts the high voltage direct current from the HV battery and the alternating current from MG1/MG2. The inverter contains a three-phase bridge circuit, which consists of 6 power transistors each for MG1 and MG2, to convert direct current and three-phase alternating current.
The HV control ECU controls the operation of the power transistors.

The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The motor inverter current sensors detect the current flowing through the V and W phase cables between the inverter and MG1/MG2. The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The HV control ECU monitors the inverter current sensors to detect a malfunction in the sensor system.

P0A72 Generator Phase V Current

P0A72 Possible Causes

  • Faulty inverter with converter assembly
  • Inverter with converter assembly harness open or shorted
  • Inverter with converter assembly circuit poor electrical connection

What Does It Mean?

How to Fix Code P0A72

Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, ejected, or corroded connector pins.

P0A72 Possible Symptoms

Check engine light illuminated (or service engine soon warning light)

P0A72 Meaning

The inverter converts the high voltage DC from the HV battery and the AC from MG1/MG2. The inverter contains a three-phase bridge circuit, which consists of 6 power transistors each for MG1 and MG2, to convert DC and three-phase AC.
The HV control ECU controls the operation of the power transistors.

The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The motor inverter current sensors detect the current flowing through the V and W phase cables between the inverter and MG1/MG2. The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The HV control ECU monitors the inverter current sensors to detect a malfunction in the sensor system.

P0A73 Generator Phase V Low Current

P0A73 Possible Causes

  • Faulty inverter with converter assembly
  • Inverter with converter assembly harness open or shorted
  • Inverter with converter assembly circuit poor electrical connection

What Does It Mean?

How to Fix Code P0A73

Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

P0A73 Possible Symptoms

Illuminated engine light (or service engine soon warning light)

P0A73 Meaning

The inverter converts the high voltage DC from the HV battery and the AC from MG1/MG2. The inverter contains a three-phase bridge circuit, consisting of 6 power transistors each for MG1 and MG2, to convert DC and three-phase AC.
The HV control ECU controls the operation of the power transistors.

The inverter transmits the necessary information for control, such as current and voltage, to the HV control ECU.
The motor inverter current sensors detect the current flowing through the V and W phase cables between the inverter and MG1/MG2. The inverter transmits the necessary information for control, such as current and voltage, to the HV control ECU.
The HV control ECU monitors the inverter current sensors to detect a malfunction in the sensor system.

P0A74 Generator Phase V High Current

P0A74 Possible Causes

  • Faulty inverter with converter assembly
  • Inverter with converter assembly harness open or shorted
  • Inverter with converter assembly circuit poor electrical connection

What Does It Mean?

How to Fix Code P0A74

Check the “possible causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

P0A74 Possible Symptoms

Check engine light illuminated (or service engine soon warning light)

P0A74 Meaning

The inverter converts the high voltage DC from the HV battery and the AC from MG1/MG2. The inverter contains a three-phase bridge circuit, consisting of 6 power transistors each for MG1 and MG2, to convert DC and three-phase AC.
The HV control ECU controls the operation of the power transistors.

The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The motor inverter current sensors detect the current flowing through the V and W phase cables between the inverter and MG1/MG2. The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The HV control ECU monitors the inverter current sensors to detect a malfunction in the sensor system.

P0A75 Generator Phase W Current

P0A75 Possible Causes

  • Faulty inverter with converter assembly
  • Inverter with converter assembly harness open or shorted
  • Inverter with converter assembly circuit poor electrical connection

What Does It Mean?

How to Fix Code P0A75

Check the “Possible Causes” listed above. Visually inspect the related cable harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

P0A75 Possible Symptoms

Engine light on (or service engine soon warning light)

P0A75 Meaning

The inverter converts the high voltage DC from the HV battery and the AC from MG1/MG2. The inverter contains a three-phase bridge circuit, consisting of 6 power transistors each for MG1 and MG2, to convert DC and three-phase AC.
The HV control ECU controls the operation of the power transistors.

The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The motor inverter current sensors detect the current flowing through the V and W phase cables between the inverter and MG1/MG2. The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The HV control ECU monitors the inverter current sensors to detect a malfunction in the sensor system.

P0A76 Generator Phase W Low Current

P0A76 Possible Causes

  • Faulty inverter with converter assembly
  • Inverter with converter assembly harness open or short-circuited
  • Inverter with converter assembly circuit poor electrical connection

What Does It Mean?

How to Fix Code P0A76

Check the “possible causes” listed above. Visually inspect the cable harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

P0A76 Possible Symptoms

Engine light on (or service engine soon warning light)

P0A76 Meaning

The inverter converts the high voltage direct current from the HV battery and the alternating current from MG1/MG2. The inverter contains a three-phase bridge circuit, consisting of 6 power transistors each for MG1 and MG2, to convert direct current and three-phase alternating current.
The HV control ECU controls the operation of the power transistors.

The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The motor inverter current sensors detect the current flowing through the V and W phase cables between the inverter and MG1/MG2. The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The HV control ECU monitors the inverter current sensors to detect a malfunction in the sensor system.

P0A77 Generator, Phase W, High Current

P0A77 Possible Causes

  • Faulty inverter with converter assembly
  • Inverter with converter assembly harness open or shorted
  • Inverter with converter assembly circuit poor electrical connection

What Does It Mean?

How to Fix Code P0A77

Check the “possible causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

P0A77 Symptoms

Possible

Engine light on (or service engine soon warning light)

P0A77 Meaning

The inverter converts the high voltage DC from the HV battery and the AC from MG1/MG2. The inverter contains a three-phase bridge circuit, consisting of 6 power transistors each for MG1 and MG2, to convert DC and three-phase AC.
The HV control ECU controls the operation of the power transistors.

The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The motor inverter current sensors detect the current flowing through the V and W phase cables between the inverter and MG1/MG2. The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The HV control ECU monitors the inverter current sensors to detect a malfunction in the sensor system.

P0A78 Drive Motor “A” Inverter Performance

P0A78 Possible Causes

  • Faulty inverter with converter assembly
  • Inverter with converter assembly harness open or short-circuited
  • Inverter with converter assembly circuit poor electrical connection

What Does It Mean?

How to Fix Code P0A78

Check the “possible causes” listed above. Visually inspect the related cable harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

P0A78 Possible Symptoms

Engine light on (or service engine soon warning light)

P0A78 Meaning

The inverter converts the high voltage direct current from the HV battery and the alternating current from MG1/MG2. The inverter contains a three-phase bridge circuit, consisting of 6 power transistors each for MG1 and MG2, to convert direct current and three-phase alternating current.
The HV control ECU controls the operation of the power transistors.

The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The motor inverter current sensors detect the current flowing through the V and W phase cables between the inverter and MG1/MG2. The inverter transmits the necessary information to perform control, such as current and voltage, to the HV control ECU.
The HV control ECU monitors the inverter current sensors to detect a malfunction in the sensor system.

P0A79 Drive Motor “B” Inverter Performance

📌 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:

  1. Visually inspect the wiring harness between the inverter and the HV ECU.
  2. Look for visible damage: worn, cut, or melted cables.
  3. Check the connectors: ensure no pins are twisted, broken, pushed out, or oxidized.
  4. Test the continuity and insulation of the circuits with a multimeter.
  5. If all the wiring appears intact, the problem may come directly from the inverter/converter – this component may require replacement if deemed faulty.
  6. 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.