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 module location on the high speed GMLAN serial data circuits
The control module B+, ignition, ground, communication enable and serial data circuit terminals

Ignition OFF, disconnect the harness connector at the K20 engine control module (ECM).
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.
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 K20 ECM for a short to ground. If the circuits test normal, replace the K20 ECM.
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 K20 ECM for a short to ground. If the circuits test normal, replace the K20 ECM.
If equipped, ignition ON, verify that a test lamp illuminates between the wakeup circuit terminal 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.
Ignition OFF, disable the high voltage system. Refer to High Voltage Disabling .
Reconnect the 12 V battery.
Ignition OFF, disconnect the X1 harness connector at the T18 battery charger.
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 1 Ω in each high speed GMLAN serial data circuit between the K20 ECM and the T18 battery charger.
- If greater than the specified range, test the serial data circuit for an open/high resistance between the K20 ECM and the T18 battery charger.
If all circuits test normal, replace the K20 ECM.