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 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.

WARNING: The Volt Battery Pack will utilize an exchange program. Please consult the most recent revision of bulletin/PI #PIP4841, available in Service Information (SI), for a list of approved Volt Battery Pack service procedures. Components that may be removed and serviced without exchanging the complete battery pack are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.

WARNING: This diagnostic has NOT been validated on-vehicle. Follow all safety protocol and utilize all appropriate personal protective equipment to ensure your safety. Failure to follow the procedures exactly as written may result in serious injury or death.

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

Control modules the vehicle is equipped with
BECM dedicated serial data circuit terminating resistors
Control module locations on the BECM dedicated serial data circuits
Each control module BECM dedicated serial data circuit terminals

Perform the High Voltage Disabling procedure before proceeding with this diagnostic. Refer to High Voltage Disabling .
Reconnect the 12 V battery.
Ignition OFF, disconnect the harness connectors with the BECM dedicated serial data circuits at an easily accessible control module that is not communicating.
Ignition ON, test for less than 4.5 V between each BECM dedicated serial data circuit at the control module that was just disconnected and ground.
- If one or more BECM dedicated serial data circuits are greater than the specified range, test the BECM dedicated serial data circuit for a short to voltage. Refer to Testing the Serial Data Circuits for a Short to Voltage .
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 greater than 100 Ω between each BECM dedicated serial data circuit at the control module connector that was just disconnected and ground.
- If one or more BECM dedicated serial data circuits are less than the specified range, test the BECM dedicated serial data circuit for a short to ground. Refer to Testing the Serial Data Circuits for a Short to Ground .
Test for 110-130 Ω between the BECM dedicated serial data circuits at the control module that was just disconnected.
- If less than 110 Ω, test for a short between the BECM dedicated serial data circuits. Refer to Testing the Serial Data Circuits for a Short Between The Circuits .
- If greater than 130 Ω, test the BECM dedicated serial data circuit for an open/high resistance. Refer to Testing the Serial Data Circuits for an Open/High Resistance .
If all serial data circuits test normal, refer to Testing the Control Module Circuits .
If all circuits test normal, replace the control module that was just disconnected.

NOTE: Some hybrid/EV battery interface control modules have a loop in the harness that connects its 5 V reference circuit back to another control circuit of the same control module. 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 control module for each of the following tests.