GM Service Manual Online
For 1990-2009 cars only

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 P0C05: Drive Motor 1 Phase U-V-W Circuit

Circuit/System Description

Each drive motor generator is controlled by a motor control module (MCM). The drive motor generators utilize 3 phase alternating current (ac) electricity. The drive motor generator 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 MCM monitors a current sensor connected to each drive motor generator phase.

Conditions for Running the DTC

    • The Hybrid Wakeup circuit is active.
    • The MCM has applied current to the drive motor generator.

Conditions for Setting the DTC

The MCM detects at least one U-V-W phase current sensor is less than 9 amps.

Action Taken When the DTC Sets

    • DTC P0C05 is a Type A DTC.
    • The hybrid powertrain control module (HPCM) commands the battery energy control module (BECM) to open the high voltage contactor relays.

Conditions for Clearing the DTC

DTC P0C05 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 Verification

  1. Clear the DTC information.
  2. Turn the ignition OFF for 1 minute.
  3. Attempt to start the engine.
  4. Retest for DTC P0C05.

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 condition 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. Disable the high voltage for servicing at the drive motor generator control module assembly cable connections. Refer to High Voltage Disabling.
  2. Inspect for damaged 3 phase cables between the drive motor generator power inverter control module (PIM) and the transmission.
  3. If damage is observed, replace the 3 phase cables.
  4. Remove the 3 phase cable assembly from the PIM distribution box. Refer to Generator Control Module 3-Phase Cable Assembly Replacement.
  5. Test the resistance of each phase by measuring between the following circuits with a DMM.
  6. • Phase U and phase V
    • Phase U and phase W
    If you meaure 0.5 ohms or less replace the drive motor generator assembly and retest for the DTC. If the DTC resets, replace the PIM.
    If you measure greater than 0.5 ohms continue with diagnosis.
  7. Remove the 3 phase cable assembly cover from the transmission and inspect the 3 phase cable terminal fasteners for the proper torque and for arc-flash damage. Refer to Generator Control Module 3-Phase Cable Assembly Replacement.
  8. If any fasteners were loose and no arc-flash damage is present, torque the fasteners and re-assembly the vehicle. Retest for the DTC.
    If any fasteners were loose and arc-flash damage is present, replace the drive motor generator assembly and the 3 phase cable assembly.
  9. Disconnect the 3 phase cable assembly from the transmission.
  10. Test each cable for continuity from the PIM connection terminal to the transmission connection terminal.
  11. If you measure greater than 0.5 ohms, replace the 3 phase cable assembly.
    If you measure 0.5 ohms or less replace the drive motor generator assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Control Module References for PIM replacement, setup, and programming.
    •  Generator Control Module 3-Phase Cable Assembly Replacement.
    •  Drive Motor Generator Rotor and Stator Removal - Unit A