GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 Sierra Denali 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 High Voltage Enabling

Danger: Ensure all High Voltage safety procedures are followed. Failure to follow the procedure exactly as written may result in serious injury or death.

Danger: Before working on any high voltage system, be sure to wear the following Personal Protection Equipment:

   • Safety glasses with appropriate side shields when within 50 feet of the vehicle, either indoors or outdoors
   • Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors
      -  Visually and functionally inspect the gloves before use.
      -  Wear the Insulation gloves at all times when working with the high voltage battery assembly, whether the system is energized or not.
Failure to follow the procedure exactly as written may result in serious injury or death.

Review the high voltage safety information prior to performing the High Voltage Enabling procedure. Refer to High Voltage Safety.

  1. Ensure that the 12 V battery is disconnected.

    2. Note: Always tighten the high voltage fasteners to the specified torque. Insufficient or excessive torque will cause malfunctions or damage.

  2. After finishing work on the high voltage systems and before reinstalling the high voltage manual disconnect lever, inspect for the following:
    3. • Verify that all tools or loose components have been removed.
    • Verify high voltage system integrity and that all connectors are installed.
    • Verify that all high voltage interlock circuit (HVIC) connectors and covers are installed.

    Object Number: 1970675 Size: SH
  3. Install the high voltage manual disconnect lever.
  4. Install the rear seat riser finish cover.
  5. Connect the 12 V battery. Refer to Battery Negative Cable Disconnection and Connection.
  6. Start the engine, then turn the ignition OFF.

    7. Note: The EBCM may set DTC C0561 71, and the DTC will not clear until the engine has been started. Refer to service bulletins for more information.

  7. Ignition ON, clear all DTC Information with a scan tool.
  8. Ignition OFF, wait 2 minutes.
  9. Ignition ON, verify with a scan tool no DTCs are set.
    10. ⇒If DTCs are set go to appropriate DTC information.
  10. Verify that High Voltage has enabled by observing the HPCM 300 V Circuit voltage scan tool parameter.
    11. ⇒If High Voltage is not enabled and no DTCs are set, return to Step 6.
  11. Start and idle the engine for 2 minutes.
  12. Ignition OFF wait 5 minutes.
  13. Ignition ON, verify with the scan tool HPCM DTC Information that the following DTCs have Ran Since Code Clear and have not set:
    14. • Contactor relay DTCs P0ADC, P0AE7 and P0AE0
    • Discharge and Pre-charge DTCs P0C76, P0C77, and P1A20
    • Motor position sensor learn DTCs P0C17 and P0C18
    • High voltage loss of isolation DTCs P1AE7, P1AF0 and P1AF2.
    ⇒If the DTCs have Ran and Passed, test drive the vehicle and verify no DTCs are set.
    ⇒If the DTCs are set, go to the appropriate DTC information.
    ⇒If the DTCs have Not Ran Since Code Clear, review and operate the vehicle according to the applicable DTC Conditions for Running and ensure the DTCs run and pass.