Volt

DTC P0A78 or P0A79

The power inverter module, often referred to as the drive motor generator power inverter module, contains the two drive motor control modules. Each motor control module operates its respective drive motor generator based upon hybrid/EV powertrain control module commands. Each motor control module controls the speed, direction and output torque of its respective drive motor generator through the sequencing actuation of high-current switching transistors called insulated gate bipolar transistors. Each insulated gate bipolar transistor assembly is monitored for fault conditions. The motor control modules are part of the power inverter module and are not serviced separately.

The high voltage contactor relays are closed.

The motor control module detects excessive current flow through the switched portion of the insulated gate bipolar transistor.

DTCs P0A78 and P0A79 are Type A DTCs.

Schematic Reference

Hybrid Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

If the DTC is set, clear DTC; Turn the vehicle OFF for 2 minutes. Turn vehicle ON, Operate vehicle within conditions for running and setting DTC. If the DTC resets, go to Circuit/System Testing.

Danger: Always perform the High-Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.

The High-Voltage Disabling procedure will perform the following tasks:

•	Identify how to disable high voltage.

•	Identify how to test for the presence of high voltage.

•	Identify conditions under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.

Failure to follow the procedures exactly as written may result in serious injury or death.
1. Perform the High Voltage Disabling procedure for servicing at the drive motor generator control module cable connections.
2. Remove the 3-phase cable assembly from the power inverter module distribution box. Refer to Drive Motor Generator Rotor and Stator Removal - Unit A or Drive Motor Generator Rotor and Stator Removal - Unit B .
3. Test for infinite resistance between the Phase Terminals listed below and earth for each phase of the appropriate M15 drive motor:

Drive Motor 1

•	X5 terminal 3-phase U

•	X5 terminal 2-phase V

•	X5 terminal 1-phase W

Drive Motor 2

•	X6 terminal 3-phase U

•	X6 terminal 2-phase V

•	X6 terminal 1-phase W

⇒	If not the specified value, test the AC circuit for a short-circuit to earth or a short-circuit between the AC circuit terminals and the aluminium cable mounting block. If the circuit tests normal, replace the T6 power inverter module. If the DTC resets replace the M15 drive motor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.