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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 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.

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 procedures exactly as written 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 each GMLAN serial data busses
    • The control modules B+, ignition, ground, communication enable and serial data circuit terminals
  1. Using the High Voltage Module Chart below, verify that the non-communicating control module is not a high voltage module. If the control module is a high voltage module, perform the High Voltage Disabling procedure before proceeding with this diagnostic. Refer to High Voltage Disabling .
  2. If high voltage disabling is required, reconnect the 12 V battery after performing the high voltage disabling procedure.
  3. Ignition OFF, disconnect the harness connector at the control module that is not communicating.
  4. 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.
  5. If equipped, ignition ON, 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.
  6. 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.
    7. NOTE: Only the high speed GMLAN modules have a serial data communication enable circuit OR an accessory wakeup serial data circuit. Either the K9 BCM or the K114B hybrid power train control module 2 is the output for these circuits. Refer to the control module schematics to identify which control modules have these circuits and which control module is the output for these circuits.
  7. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup circuit terminal coming from the K9 BCM and ground.
    • If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 BCM, for an open/high resistance or short to ground. If the circuits test normal, replace the K9 BCM.
  8. If equipped, ignition ON, verify that a test lamp illuminates between the accessory wakeup circuit terminal coming from K114B hybrid powertrain control module 2 and ground.
    • If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K114B hybrid powertrain control module 2, for an open/high resistance or short to ground. If the circuits test normal, replace the K114B hybrid powertrain control module 2.
    9. NOTE: Only the high voltage energy high speed GMLAN modules have a high voltage energy serial data communication enable circuit, and the K114B hybrid power train control module 2 is the output for this circuit. Refer to the control module schematics to identify which control modules have this circuit.
  9. If equipped, ignition ON, verify that a test lamp illuminates between the high voltage energy communication enable circuit terminal coming from K114B hybrid powertrain control module 2 and ground.
    • If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K114B hybrid powertrain control module 2, for an open/high resistance or short to ground. If the circuits test normal, replace the K114B hybrid powertrain control module 2.
  10. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 Ω between each serial data circuit terminal and the appropriate data link connector (DLC) terminal listed below:
    • X84 DLC class 2 serial data circuit terminal 2
    • X84 DLC low speed GMLAN serial data circuit terminal 1
    • X84 DLC high speed GMLAN serial data circuit terminal 6 or 14
    • X84 DLC mid speed GMLAN serial data circuit terminal 3 or 11
    • X84 DLC chassis high speed GMLAN serial data circuit terminal 12 or 13
    • X84B auxiliary data connector powertrain high speed GMLAN serial data circuit terminal 12 or 13
    • X84B auxiliary data connector high voltage energy high speed GMLAN serial data circuit 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 the control module setting the DTC or a serial data splice pack.
  11. If all circuits test normal, replace the control module that is not communicating.
High Voltage Module Chart

Module Voltage System Data Link Type
T6 Power Inverter Module (Includes Drive Motor Control Modules 1, 2, 3 and K114A Hybrid Powertrain Control Module 1) 300 V
12 V
  • Powertrain High Speed GMLAN
  • Chassis High Speed GMLAN
  • High Speed GMLAN
K1 14 V Power Module 300 V
12 V		 Powertrain High Speed GMLAN
G1 A/C Compressor 300 V
12 V		 High Speed GMLAN
K16 Battery Energy Control Module (BECM) 300 V
12 V
  • High Voltage Energy High Speed GMLAN
  • High Speed GMLAN
K112A, K112B, K112C, K112D Hybrid Battery Interface Control Modules 1, 2, 3, and 4 300 V
12 V
  • High Voltage Energy High Speed GMLAN
  • High Speed GMLAN
T18 Battery Charger 300 V
12 V
  • High Voltage Energy High Speed GMLAN
  • High Speed GMLAN
K10 Coolant Heater Control Module 300 V
12 V		 Low Speed GMLAN
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