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Home >> Cadillac >> 2012 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 1220 (Hybrid Engine Control System) >> Diagnostic Information and Procedures >> DTC P1AF0 or P1AF2 >> Circuit/System Testing
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Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
    IMPORTANT: DTC P1AE7 must test and pass before performing this diagnostic procedure.
  1. Inspect for DTC P1AE7.
    • If the DTC is set, the loss of isolation has occurred within the drive motor generator battery. Refer to DTC P1AE6 or P1AE7 .
  2. Inspect for DTCs P0A78, P0A79, P0BFD, P0BFE, P0C01, or P0C04.
  3. Place the vehicle in the following condition:
    • Ignition OFF for at least 2 minutes
    • Hood Closed
    • Transmission in Park
    4. IMPORTANT: The following sequence must be accomplished within the time stated in Conditions for Setting the DTC.
  4. Turn the ignition ON with the engine OFF.

    Observe and record the scan tool HPCM 300V Circuit Voltage parameter. High voltage should be enabled and Hybrid Battery voltage observed.

    Compare the HPCM 300V Circuit Voltage parameter value to the MCM 1 Isolation Voltage display and MCM 2 Isolation Voltage display. With no loss of isolation currently present, these values should all be within 20V of each other.

    • If ONLY ONE MCM Isolation Voltage value is not within the indicated range, replace the PIM.
    • If BOTH MCM Isolation Voltage values are not within the indicated range, continue to the next step.
    • If BOTH MCM Isolation Voltage values are within the indicated range, a loss of isolation condition is not currently present. Proceed to Drive Motor Generator Phase Testing below.
    5. WARNING: 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.
  5. Perform the High Voltage Disabling procedure for servicing at the drive motor generator control module cable connections.
  6. Remove the air conditioning control module (ACCM) high voltage cable connector from the drive motor generator power inverter module (PIM).

    Protect the terminal ends immediately with the EL-48569  terminal covers and UL® Listed or equivalent insulation tape rated at a minimum of 600 volts.

  7. Temporarily install the PIM high voltage distribution cover.
  8. Install the drive motor generator control module sight shield.
  9. Install the high voltage manual disconnect lever.
  10. Connect the 12 volt battery. Refer to Battery Negative Cable Disconnection and Connection .
  11. Place the vehicle in the following condition:
    • Hood Closed
    • Transmission in Park
    12. IMPORTANT: The following sequence must be accomplished within the time stated in Conditions for Setting the DTC.
  12. Turn the ignition ON with the engine OFF.

    Observe and record the scan tool HPCM 300V Circuit Voltage parameter. High voltage should be enabled and Hybrid Battery voltage observed.

    Compare the HPCM 300V Circuit Voltage parameter value to the MCM 1 Isolation Voltage display. With no loss of isolation currently present, these values should be within 20V of each other.

    • If the values are not within the indicated range, continue to the next step.
    • If the values are within the indicated range, replace the ACCM.
    13. WARNING: 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.
  13. Perform the High Voltage Disabling procedure for servicing at the drive motor generator control module cable connections.
  14. Remove the high voltage Battery Positive and Negative Cable Assembly (300V) connector from the drive motor generator power inverter module (PIM). Remove and retain the cable mounting block O-ring. Re-install the O-ring after testing is complete.
  15. Connect the EL-48458  to the Battery Positive and Negative Cable Assembly (300V) and the PIM connector X1 and Close the high voltage contactor relays. See Special Tools . Refer to High Voltage System Diagnosis (EL-48458)  for Installation Procedure and usage instructions.
    16. IMPORTANT: This scan tool output control could cause a loss of communication condition with the battery energy control module (BECM). In order to clear this condition you must remove the BECM fuse from the auxiliary fuse block. To avoid causing this BECM condition, ensure the following conditions are met prior to activating the scan tool output control:
  16. Activate the BECM 300V Isolation Test output control with the scan tool. Observe the 300V Isolation Test Status scan tool parameter. The Isolation Test should complete within 1 minute.
    • If the 300V Isolation Test Status parameter indicates a Passed condition, replace the PIM and Accessory DC Power Control Module (APM).
    • If the 300V Isolation Test Status parameter indicates a Failed condition, continue to the next step.
  17. Disconnect the EL-48458  from the vehicle. See Special Tools . Refer to High Voltage System Diagnosis (EL-48458)  for Removal Procedure.
    18. WARNING: 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.
  18. Perform the High Voltage Disabling procedure for servicing at the drive motor generator battery.
  19. Remove the high voltage Battery Positive and Negative Cable Assembly (300V) connector from the drive motor generator battery assembly.

    Protect the terminal ends immediately with the EL-48569  terminal covers and UL® Listed or equivalent insulation tape rated at a minimum of 600 volts.

    20. IMPORTANT: The drive motor generator control module sight shield and the drive motor generator battery terminal cover must be reinstalled in order to complete the HVIC current loop. The BECM will not close the high voltage contactor relays if an open HVIC condition is observed.
  20. Connect the EL-48458  to the hybrid battery high voltage terminals and PIM connector X1 with the EL-48458  harnesses. See Special Tools . Close the high voltage contactor relays. Refer to High Voltage System Diagnosis (EL-48458)  for usage and set-up instructions.
    21. IMPORTANT: This scan tool output control could cause a loss of communication condition with the battery energy control module (BECM). In order to clear this condition you must remove the BECM fuse from the auxiliary fuse block. To avoid causing this BECM condition, ensure the following conditions are met prior to activating the scan tool output control:
  21. Activate the BECM 300V Isolation Test output control with the scan tool. Observe the 300V Isolation Test Status scan tool parameter. The Isolation Test should complete within 1 minute.
    • If the 300V Isolation Test Status indicates a Passed condition, replace the Battery Positive and Negative Cable Assembly (300V).
    • If the 300V Isolation Test Status indicates a Failed condition, the loss of isolation has occurred within the hybrid battery between the switched side of the high voltage contactors and the hybrid battery high voltage terminal assembly. Replace or repair the Hybrid Battery assembly as applicable.

Drive Motor Generator Phase Testing

    WARNING: 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. 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 PIM distribution box. Refer to Generator Control Module 3-Phase Cable Assembly Replacement .
  3. Test the resistance to ground for each phase of both drive motor generators by measuring between the following points with a DMM. You should measure infinite resistance.
    • Phase U terminal and chassis ground
    • Phase V terminal and chassis ground
    • Phase W terminal and chassis ground
    • If infinite resistance is measured, a measurable loss of isolation is not currently present. Reassemble the vehicle and retest for DTCs.
    • If less than the specified value, continue with Circuit/System Testing.
  4. Remove the 3-phase cable assembly from the transmission. Refer to Generator Control Module 3-Phase Cable Assembly Replacement . Ensure the terminals are not contacting chassis ground.
  5. Retest the resistance to ground for each phase of the 3-phase cable. Measure between the following points with a DMM. You should measure infinite resistance.
    • Phase U terminal and chassis ground
    • Phase V terminal and chassis ground
    • Phase W terminal and chassis ground
    • If infinite resistance is measured, replace the applicable drive motor generator.
    • If less than the specified value, replace the generator control module 3-phase cable assembly.
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