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Circuit/System 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 includes the following steps:

  • 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.

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

  • Safety glasses with appropriate side shields when within 15 meters (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 with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not.

Failure to follow the procedures may result in serious injury or death.

NOTE:

Use the schematic to identify the following:

  • Control modules the vehicle is equipped with
  • Control module locations on the low and high speed GMLAN serial data circuits
  • The control modules B+, ignition, ground, communication enable and serial data circuit terminals
  1. Determine the control module that is not communicating. Refer to Control Module U Code List .
  2. Using the Hybrid High Voltage Module Chart below, verify that the non-communicating control module is not a high voltage module.
  3. If high voltage disabling is required, reconnect the 12 V battery after performing the high voltage disabling procedure.
  4. Ignition OFF, disconnect the harness connector of the control module that is not communicating.
  5. Test for less than 10 Ω between each ground circuit terminal and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  6. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
  7. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
    8. NOTE:

    Only the high speed GMLAN modules have a serial data communication enable circuit OR an accessory wakeup serial data circuit, and the BCM is the output for these circuits. Refer to the module schematics to identify which modules have these circuits.

  8. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup circuit terminal and ground.
    • If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM.
  9. Ignition OFF, all access doors closed, all vehicle systems OFF, and key out of ignition switch. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 Ω between the serial data circuit terminals and the appropriate DLC terminal listed below:
    • Class 2 serial data circuit terminal 2
    • Low speed GMLAN serial data terminal 1
    • High speed GMLAN serial data terminal 6 or 14
    • Powertrain high speed GMLAN serial data terminal 3 or 11
    • If greater than the specified range, test the serial data circuit for an open/high resistance between the non communicating control module and a control module setting the DTC or a serial data splice pack.
  10. If all circuits test normal, replace the control module that is not communicating.
Hybrid High Voltage Module Chart

Module Voltage System Data Link Type
Drive Motor Generator Power Inverter Module (PIM) (Includes Drive Motor Control Module (MCM) 1, 2 and Hybrid Powertrain Control Module (HPCM) 300 V
12 V
  • High Speed Hybrid GMLAN
  • High Speed GMLAN
Accessory DC Power Control Module (APM) 300 V
42 V
12 V		 High Speed Hybrid GMLAN
Transmission Control Module (TCM) (RPO M99) 300 V
12 V		 High Speed GMLAN
Air Conditioning Control Module (ACCM) (Part of AC Compressor with HP2) 300 V
12 V		 Low Speed GMLAN
Drive Motor Generator Battery Control Module (BECM) 300 V
12 V		 High Speed GMLAN
Power Steering Control Module (PSCM) 42 V
12 V		 High Speed GMLAN
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