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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.

WARNING:

The eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI# PIC5520, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.

NOTE:

Use the schematic to identify the following:

  • Devices the vehicle is equipped with
  • Device locations on the serial data circuit
  • The device's ground, B+, ignition, ground, accessory wakeup serial data, serial data communication enable, and serial data circuit terminals
  1. Perform the High Voltage Disabling procedure before proceeding with this diagnostic if the non communicating control module is a high voltage module from the following list. Refer to High Voltage Disabling .
    • K16 Battery Energy Control Module
    • K59 Starter/Generator Control Module
  2. If high voltage disabling is required, reconnect the 12V battery after performing the high voltage disabling procedure.
  3. Ignition OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 meters (9.8 feet) away from vehicle. Disconnect all the harness connectors at the device that is not communicating. It may take up to 2 minutes for all vehicle systems to power down.
  4. Test for less than 10Ω between each ground circuit terminal and ground.
    • If 10Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2Ω in the ground circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, repair the open/high resistance in the ground connection.
    • If less than 10Ω 
  5. Ignition ON.
  6. If equipped, verify a test lamp illuminates between each B+ circuit terminal and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF.
    2. Test for less than 2Ω in the B+ circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF.
    2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the disconnected device.
    • If the test lamp illuminates 
  7. Ignition ON.
  8. If equipped, verify a test lamp illuminates between each ignition circuit terminal and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF.
    2. Test for less than 2Ω in the ignition circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, verify the fuse is OK and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF.
    2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the disconnected device.
    • If the test lamp illuminates 
  9. Ignition ON.
  10. If equipped, verify a test lamp illuminates between each ignition circuit terminal, which is controlled by a control module, and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the harness connectors at the control module that controls the ignition circuit.
    2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2Ω in the ignition circuit end to end.
      • If 2Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2Ω, replace the control module that controls the ignition circuit.
    • If the test lamp illuminates 
    11. NOTE:

    This test step is only applicable to low speed GMLAN devices.

  11. Test for less than 4.5V between each low speed GMLAN serial data circuit terminal and ground.
    • If less than 4.5V 
  12. Ignition OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 meters (9.8 feet) away from vehicle. It may take up to 2 minutes for all vehicle systems to power down.
  13. Test for less than 2Ω in each of the serial data circuits end to end between the device harness connector and the X84 data link connector terminals listed below.
    • Low speed GMLAN serial data circuit terminal 1
    • High speed GMLAN serial data circuit terminal 6 or 14
    • Mid speed GMLAN serial data circuit terminal 3 or 11
    • Chassis high speed GMLAN serial data circuit terminal 12 or 13
    • If 2Ω or greater 

      Repair the open/high resistance in the serial data circuit between the non communicating device and the device setting the DTC or a serial data splice pack.

    • If less than 2Ω 
    14. NOTE:

    The following test step is only applicable to high speed GMLAN devices.

  14. Test for 110-130Ω between each pair of high speed GMLAN serial data circuits.
    • If between 110-130Ω 
  15. Replace the device that is not communicating.
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