Circuit/System Testing: Notes

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:

Each device may need to be disconnected to isolate a circuit fault. Use the schematic to identify the following:

Powertrain high speed GMLAN devices the vehicle is equipped with
Powertrain high speed GMLAN serial data circuit terminating resistors
Device locations on the powertrain high speed GMLAN serial data circuits
Each device's ground, B+, ignition and powertrain high speed GMLAN serial data circuit terminals

Some devices with an internal terminating resistor have a loop in the harness that connects the internal terminating resistor to the serial data circuit. When wired this way, test these loop circuits for the appropriate failure mode short to voltage, short to ground or open/high resistance prior to replacing the device for each of the following tests.

Perform the High Voltage Disabling procedure. Refer to High Voltage Disabling .
Reconnect the 12 V battery.
Ignition/Vehicle OFF, disconnect the harness connectors with the powertrain high speed GMLAN serial data circuits at an easily accessible device that is not communicating. Refer to Data Link References to determine which devices are on the powertrain expansion bus.
Ignition ON/Vehicle In Service Mode.
Test for less than 4.5 V between each powertrain high speed GMLAN serial data circuit at the device that was just disconnected and ground.
- If 4.5 V or greater
  Refer to Testing the Serial Data Circuits for a Short to Voltage.
- If less than 4.5 V
Ignition/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.
Test for greater than 100 Ω between each powertrain high speed GMLAN serial data circuit at the device that was just disconnected and ground.
- If 100 Ω or less
  Refer to Testing the Serial Data Circuits for a Short to Ground.
- If greater than 100 Ω
Test for 110 - 130 Ω between each pair of the powertrain high speed GMLAN serial data circuits at the device that was just disconnected:
- If less than 110 Ω
  Refer to Testing the Serial Data Circuits for a Short between the Circuits.
- If greater than 130 Ω
  Refer to Testing the Serial Data Circuits for an Open/High Resistance.
- If between 110 - 130 Ω
Refer to Testing the Device Circuits.