Service Information

Volt

DTC P0C28

Diagnostic Instructions

•	Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

•	Review Strategy Based Diagnosis for an overview of the diagnostic approach.

•	Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0C28: Auxiliary Transmission Fluid Pump High Current

The power inverter module, often referred to as the drive motor generator power inverter module, contains three motor control modules and the hybrid powertrain control module. Two of the motor control modules operate their respective drive motor generator based upon drive motor generator power inverter module commands. The third motor control module controls the Auxiliary Transmission Fluid Pump Motor. The motors utilise 3 phase AC electricity. The motor stator coil is comprised of three-phase circuits. The phase circuits are identified as phase U, phase V and phase W. The U-V-W phase circuits are connected in a wye configuration. This means each phase is connected at a single, central point. The motor control modules monitor a current sensor connected to each motor phase. The current sensor is part of the motor assembly and is not serviced separately. The motor control modules are part of the power inverter module and are not serviced separately.

Conditions for Running the DTC

Vehicle is ON.

Conditions for Setting the DTC

One or more phase currents are greater than 35 A.

Action Taken When the DTC Sets

•	DTC P0C28 is a Type A DTC.

•	Vehicle propulsion will be disabled.

Conditions for Clearing the DTC

DTC P0C28 is a Type A DTC.

Reference Information

Schematic Reference

Hybrid Controls Schematics

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

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.

Perform the High Voltage Disabling procedure for servicing the T6 power inverter module or T12 transmission.
Disconnect the X8 connector from the T6 power inverter module.
Test for infinite resistance between the terminals listed below and each for each phase of the G5 auxiliary transmission fluid pump:

•	X8 terminal 3 phase U

•	X8 terminal 2 phase V

•	X8 terminal 1 phase W

⇒	If less than the specified value, replace the G5 auxiliary transmission fluid pump.

Replace the T6 power inverter module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Auxiliary Fluid Pump Motor and Fluid Pump Disassemble and Auxiliary Fluid Pump Motor and Fluid Pump Assemble for auxiliary transmission fluid pump replacement.

•	Control Module References for Drive Motor Generator Power Inverter Module, also called the power inverter module, replacement, programming and set-up.