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 Descriptors

DTC P1AF8: Drive Motor 1 Control Module Shutdown Performance

DTC P1AFE: Drive Motor 2 Control Module Shutdown Performance

Circuit/System Description

The drive motor generator power inverter control module (PIM) contains two motor control modules (MCMs) and the hybrid powertrain control module (HPCM). Each MCM operates its respective drive motor generator based upon HPCM commands. Each MCM 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 (IGBTs). Each drive motor generator operates utilizing 3 phase alternating current (ac) electricity. Each IGBT operates a single phase of the drive motor generator. Each phase is individually identified as U, V and W. Each MCM monitors the current of each phase in order to detect PIM overcurrent conditions.

When high voltage is enabled, each MCM supplies its respective drive motor generator with just enough current to energize the magnetic field even when no motor generator torque is required. The MCM monitors the phase current sensors for this minimal current to ensure the drive motor phase circuits are functioning properly.

Conditions for Running the DTC

    • The ignition is ON.
    • Ignition voltage is 8-18 volts.

Conditions for Setting the DTC

The control module has detected a phase current fault.

Action Taken When the DTC Sets

    • DTCs P1AF8 and P1AFE are Type A DTCs.
    • The HPCM commands the battery energy control module (BECM) to open the high voltage contactor relays.

Conditions for Clearing the DTC

DTCs P1AF8 and P1AFE are Type A DTCs.

Diagnostic Aids

    • An intermittent loss of battery power to the drive motor generator power inverter control module (PIM) may set this DTC.
    • An open 3 phase circuit, prior to ignition ON, may set this DTC.

Reference Information

Schematic Reference

Hybrid Controls Schematics

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. Turn the ignition ON.
  4. Retest for DTC P1AF8 or P1AFE.

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 PIM and the transmission.
  3. If damage is observed, replace the 3 phase cables.
  4. Inspect the 3 phase cable terminal fasteners for the proper torque and for arc-flash damage.
  5. If any fasteners were loose and no arc flash damage is present, torque the fasteners and re-assemble the vehicle. Retest for the DTC.
    If any fasteners were loose and arc flash damage is present, replace the PIM and the 3 phase cable assembly.
  6. Remove the 3 phase cable assembly from the PIM distribution box. Refer to Generator Control Module 3-Phase Cable Assembly Replacement.
  7. Test the resistance of each phase by measuring between the following circuits with a DMM.
  8. • Phase U and phase V
    • Phase U and phase W
    If you measure 0.5 ohms or less, replace the applicable drive motor generator assembly and retest for the DTC. If the DTC resets, replace the PIM.
    If you measure more than 0.5 ohms, continue with diagnosis.
  9. 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.
  10. If any fasteners were loose and no arc flash damage is present, torque the fasteners and re-assemble the vehicle. Retest for the DTC.
    If any fasteners were loose and arc flash damage is present, replace the applicable drive motor generator assembly and the 3 phase cable assembly.
  11. Disconnect the 3 phase cable assembly from the transmission. Refer to Generator Control Module 3-Phase Cable Assembly Replacement.
  12. Test each cable for continuity from the PIM connection terminal to the transmission connection terminal.
  13. If you measure greater than 0.5 ohms, replace the 3 phase cable assembly.
    If you measure 0.5 ohms or less, replace the applicable 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 or Drive Motor Generator Rotor and Stator Removal - Unit B