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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 schematics and connector end views to identify the device's ground, B+, ignition, accessory wake up serial data, serial data communication enable, accessory wake up serial data 2, high voltage energy management communication enable, and serial data circuit terminals.

  1. Using the High Voltage Device Chart below, verify that the non-communicating device is not a high voltage device. If the device is a high voltage device, 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. Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 2 min for all vehicle systems to power down. Disconnect all the harness connectors at the device that is not communicating.
  4. Test for less than 10 Ω between each ground circuit terminal and ground.
    • If 10 Ω or greater 
    1. Vehicle OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • If less than 10 Ω 
  5. Vehicle in Service Mode.
  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. Vehicle OFF, remove the test lamp.
    2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, 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. Vehicle OFF, remove the test lamp.
    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. 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. Vehicle OFF, remove the test lamp.
    2. Test for less than 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, 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. Vehicle OFF, remove the test lamp.
    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 
  8. 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. Vehicle OFF, remove the test lamp, 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 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the control module that controls the ignition circuit.
    • If the test lamp illuminates 
  9. Test for less than 4.5 V between each GMLAN serial data circuit terminal and ground.
    • If less than 4.5 V 
  10. Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 2 min for all vehicle systems to power down.
  11. Test for greater than 100 Ω between each GMLAN serial data circuit terminal and ground.
    • If greater than 100 Ω 
  12. Test for less than 2 Ω in each of the serial data circuits end to end between the device harness connector and the appropriate X84 Data Link Connector terminals listed below:
    • X84 DLC low speed GMLAN serial data circuit terminal 1
    • X84 DLC high speed GMLAN serial data circuit terminal 6 or 14
    • X84 DLC object high speed GMLAN serial data circuit terminal 3 or 11
    • X84 DLC chassis high speed GMLAN serial data circuit terminal 12 or 13
    • If 2 Ω 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 2 Ω 
    13. NOTE:

    The following test step is only applicable to a high speed GMLAN device with 2 pairs of serial data circuits or a high speed GMLAN device with an internal terminating resistor.

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

Device Voltage System Data Link Type
K16 Battery Energy Control Module (BECM) 300 V
12 V
  • High Voltage Energy Management High Speed GMLAN
  • High Speed GMLAN
  • BECM Dedicated Bus
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